Nature Unbound III: Holocene climate variability (Part A)

Summary: Holocene climate is characterized by two initial millennia of fast warming followed by four millennia of higher temperatures and humidity, and a progressively accelerating cooling and drying for the past six millennia. These changes are driven by variations in the obliquity of the Earth’s axis. The four millennia of warmer temperatures are called the Holocene Climatic Optimum which was 1-2°C warmer than the Little Ice Age. This climatic optimum was when global glaciers reached their minimum extent. The Mid-Holocene Transition, caused by orbital variations, brought a change in climatic mode, from solar to oceanic dominated forcing. This transition displaced the climatic equator, ended the African Humid Period and increased El Niño activity.

Introduction

A review of abrupt climate changes of the recent past provides a frame of reference for current global warming. The glacial cycle was reviewed in the first article in the series. The second article focused on the Dansgaard-Oeschger cycle that characterizes glacial periods. In this article I review the general features of Holocene climate, limiting it to the period ending in the 0 yr BP (year zero before present), that is established by geologists and paleoclimatologists as 1950.

As we saw in the previous article, botanists studying peat stratigraphy were among the first to notice, in the late 19th and early 20th century, abrupt climate changes reflected in peat layers. These sudden transitions were later confirmed by changes in sediment pollen composition. Scandinavian palynologists established the Blytt-Sernander sequence which divided the Holocene into five periods. They used the terms Boreal for drier, and Atlantic for wetter (figure 33).

Figure 33. Pollen diagram at Roskilde Fjord. An example of the Blytt-Sernander climatic zones established with the traditional pollen indicators, with the distinct elm-fall at the Atlantic/Sub-Boreal transition, and the rise of beech at the Sub-Boreal/Sub-Atlantic transition. Period dates might change at different locations. Source: N. Schrøder et al. 2004. J. Transdiscip. Environ. Stud. 3 1-27.

The Blytt-Sernander sequence fell out of fashion in the 1970s when new techniques allowed a more quantitative reconstruction of past climates. However, it captures the essence of Holocene climate as four periods of roughly 2500 years each. Every period shows a characteristic vegetation pattern indicative of stable climatic conditions, separated from other periods by rapid vegetation changes suggestive of abrupt climate changes. The dates and conditions generally accepted (Encyclopedia of Environmental Change) are:

The transition from Sub-Boreal to Sub-Atlantic took place at the end of the Bronze Age. Rutger Sernander proposed that this climatic change was abrupt, even a catastrophe that he identified with the Fimbulwinter of the Sagas. At the time other scientists believed in a more gradual climatic change, but recent studies on the 2.8 kyr abrupt cooling event (Kobashi et al., 2013) agree with Sernander.

Another classification divides the Holocene climatically into two periods: the Holocene Climatic Optimum (HCO, also known as Hypsithermal or Holocene Thermal Maximum), between 9,000 and 5,500 yr BP (although some authors only consider it from 7,500 yr BP after the 8.2 kyr event), and the Neoglacial period, between 5,000 and 100 yr BP, separated by the Mid-Holocene Transition (MHT) that roughly coincides with the start of the Bronze Age.

Finally other authors divide the Holocene in three periods. The Early Holocene, up to the 8.2 Kyr event, the Middle Holocene, between the 8.2 and the 4.2 Kyr events, and the Late Holocene since the 4.2 Kyr event. Although this is currently the most popular subdivision, in my opinion, it fails to properly capture the climatic trends of the Holocene.

Holocene general climate trend

Broadly speaking the Holocene had an abrupt start at 11,700 yr BP, after the Younger Dryas cold relapse, and reached maximal temperatures in about 2,000 years. Since about 9,500 yr BP, a time that coincides with maximal obliquity of the Earth axis, the climate of the Holocene stopped warming and a few thousand years later started a progressive cooling.

By far the main factor driving Holocene climatic change are the insolation changes due to the orbital variations of the Earth (figure 34). These changes are of two types that produce two different effects not always properly differentiated by Holocene climate researchers. Changes due to precession (modulated by eccentricity) have the effect of redistributing insolation between the different seasons of the year by latitude. The 23,000-year precession cycle determines the direction each hemisphere is pointing towards at perihelion and aphelion, and thus the amount of insolation received by each hemisphere at any point of the orbit. Insolation changes due to precession are represented in figure 34 with three month insolation curves for a North and South latitude, relative to present values. These changes increase or decrease seasonality or the difference between summer and winter. So, Northern Hemisphere seasonality was minimal at the Last Glacial Maximum, and maximal at the start of the Holocene, 10,500 yr BP, and will become minimal again in a thousand years.

Precession changes do not alter the annual amount of insolation at any latitude, since whatever insolation they take from one month at a particular location, they give back in another month within the same year. Precession changes are also asymmetrical, as their effect is opposite in each hemisphere, so the Northern Hemisphere summer (June-August, N-JJA thick red line in figure 34) has become progressively cooler during most of the Holocene, while Southern Hemisphere summer (December-February, S-DJF thick blue line in figure 34) has become progressively warmer during most of the Holocene. Precession changes are responsible for sea surface temperature (SST) patterns, and thus oceanic currents. North-South differences set the position of the ITCZ (Intertropical Convergence Zone or the climatic equator). Therefore they are responsible for the African Humid Period, monsoon patterns and the important Mid-Holocene Transition (MHT), that changed the climate mode of the Holocene globally.

Figure 34. Insolation changes due to orbital variations of the Earth. The insolation changes for the last 40,000 years are represented. Black temperature proxy curve represents δ18O isotope changes from NGRIP Greenland ice core (without scale). The insolation curves are presented as the insolation anomaly for summer, winter, spring, and fall. N (red) or S (blue) are the Northern or Southern Hemisphere and the three letters are the month initials. Northern and southern summer insolation represented with thick curves. Background color represents changes in annual insolation by latitude and time due to changes in the Earth’s axial tilt (obliquity), shown in a colored scale. This figure essentially shows how global temperature changes respond mainly to persistent changes in insolation caused by changes in obliquity that are symmetrical for both poles. Changes in seasonality insolation caused by the precession cycle (modified by eccentricity) are asymmetric and less important for the global response, although they cause profound changes in regional climatic differences. The Holocene Climatic Optimum corresponds to high insolation surplus in polar latitudes (red area), while Neoglacial conditions represent the first 5,000 years of a 10,000 year drop into a high glacial insolation deficit in polar latitudes (blue area). Sources: Insolation curves: P.J. Polissar et al. 2013. PNAS Vol. 110 No. 36 pp. 14551–14556. NGRIP δ18O isotope curve: NGRIP members. 2004. Nature, 431, 147-151. Background color: Steve Carson. The science of Doom.

Changes due to obliquity have the effect of redistributing insolation between different latitudes following an obliquity cycle of 41,000 years. When obliquity was maximal 9,500 years ago, both poles received more insolation due to obliquity, while the tropics received less. Obliquity also affects seasonality, at maximal axial tilt, there is an increased difference between summer and winter at high latitudes. But unlike precession changes, obliquity alters the amount of annual insolation at different latitudes in a 41,000 year cycle. This is represented by the background color of figure 34, that shows how the polar regions received increasing insolation from 30,000 yr BP to 9,500 yr BP. Since then, and for the next 11,500 years, the poles will be receiving decreasing insolation. Unlike precessional insolation changes, obliquity changes are symmetrical. Although the annual insolation change is not too large, it accumulates over tens of thousands of years and the total change is staggering, creating a huge insolation deficit or surplus. This changes the equator-to-pole temperature gradient, and is largely responsible for entering and exiting glacial periods (Tzedakis et al., 2017) and for the general evolution of global temperatures and climate during the Holocene. Obliquity changes contribute to the lack of warming of Antarctica during the Holocene, despite increasing Southern Hemisphere summer insolation. Ultimately obliquity changes will be responsible for the glacial inception that will put an end to the Holocene interglacial in the distant future.

In the Holocene, the precession cycle and the obliquity cycle are almost aligned so that maximal obliquity and maximal northern summer insolation are almost coincident at the beginning of the interglacial about 10,000 years ago. See in figure 34 how the thick red curve representing northern summer insolation reaches maximal values 10 kyr BP, almost coinciding with the center of the background polar red color, representing highest warming from maximal obliquity about 9.5 kyr BP. However this has an interesting consequence. 19,000 years ago obliquity was the same as it is now (only increasing), and the precession cycle was at the same position as it is now (same 65 °N summer insolation; figure 34). The Earth was receiving the same energy from the Sun, and the orbital configuration was distributing it over the planet in the same way during the Last Glacial Maximum as today. Why is the climate so different for the same energy input?

The answer is the huge thermal inertia of the planet due mainly to its water content. 21,000 years ago the increasing obliquity had been adding energy to the poles for 10,000 years, reducing the insolation latitudinal gradient (Raymo & Nisancioglu, 2003), and adding energy to the summers (Huybers, 2006; Tzedakis et al., 2017), and was on its way to overcome the huge cold inertia with the help of precession changes that were about to take place. In the present, decreasing obliquity has been taking energy from the poles for 10,000 years, increasing the insolation latitudinal gradient that favors energy loss and increased polar precipitation, and reducing energy during summers. These changes will also overcome the huge warm inertia even against precession changes, but will do so progressively for many thousands of years. A comparison between temperatures and obliquity over the past 800,000 years shows that while variable, the thermal inertia of the planet delays the temperature response to obliquity changes by an average of 6,500 years (figure 35).

On a multi-millennial scale, global average temperatures follow mainly the 41,000 year obliquity cycle with a lag of several thousand years. Holocene temperatures are no exception, and a few thousand years after the peak in obliquity (9,500 years ago), temperatures started to decline. This general pattern of Holocene temperatures was already known by the late 1950’s from a variety of proxy records from different disciplines (Lamb, 1977; figure 36 A). Greenland ice cores confirmed this pattern, when corrected for uplift (Vinther et al., 2009), and greatly improved the dating of temperature changes (figure 36 B).

There is only one Holocene global average temperature reconstruction available (Marcott et al., 2013; figure 37 a). To correct some of the problems it presents, I use this reconstruction averaged by differencing (explained here), without any smoothing, and with the original published dates for the proxies. I have also rescaled the temperature changes to make them congruent with the vast literature and consilience of evidence from different fields that indicates that the Holocene Climatic Optimum was on average between 1 and 2 °C warmer than the Little Ice Age (figure 37 b). This rescaling is discussed below. The resulting temperature curve is extraordinarily similar to H. Lamb regional reconstruction from the 1970s (figure 36 A), with significant temperature drops at 5.5, 3, and 0.5 kyr BP.

What role, if any, have greenhouse gases (GHG) played in Holocene climate change? Available data indicates that despite significant changes in GHG concentration in the atmosphere during the period of 10,000 to 600 yr BP, their contribution to temperature changes cannot have been important.

According to Monnin et al. (2004), CO2 concentrations measured in Antarctic ice cores decreased from 267 to 258 ppm between 10,000 and 6,800 yr BP, and afterwards increased more or less linearly to 283 ppm by 600 yr BP, just prior to the LIA (figure 38). This increase of 25 ppm represents about 10% of a doubling. Consider the period from the Last Glacial Maximum (20 kyr BP) to the HCO when atmospheric CO2 increased from 70 ppm or 36% of a doubling. We can see that the Holocene CO2 increase constitutes 27% of the CO2 increase from the coldest point of the last glacial period to the warmest point of the present interglacial. Almost a third of the glacial-interglacial span cannot be considered insignificant for the increase in CO2 that took place between 6,800 and 600 yr BP. If CO2 is as potent warming agent as purported in some theories and models, one should expect some warming coming out of this CO2 increase, especially because from 5,000 yr BP it was accompanied by an increase in atmospheric CH4 concentrations (Kobashi et al., 2007; figure 38). But instead of an increase in temperatures, what we find is a progressive decrease from the HCO to the LIA driven by changes in insolation.

Climate models adjusted to explain present global warming do not reproduce the Holocene climate. The mean temperatures of an ensemble of three models (CCSM3, FAMOUS, and LOVECLIM; Liu et al., 2014; figure 38) show a constant increase in temperatures during the entire Holocene, driven by the increase in GHG. This disagreement between models and data-derived reconstructions of Holocene climate has been termed by the authors the Holocene temperature conundrum (Liu et al., 2014).

Climate modelers should take the opportunity to adjust their models to Holocene conditions. It is clear that the main driver of Holocene climate has been changes in insolation due to orbital variation. Changes in GHG concentrations appear to have had only a minor effect.

The Holocene Climatic Optimum

The issue of Holocene temperatures has become controversial. While the Holocene Hypsithermal or Climatic Optimum (HCO, ~ 9800-5700 BP) is well characterized in the Northern Hemisphere as 1-5°C warmer than the bottom of the LIA depending on latitude, much less information exists regarding the tropical and Southern areas. Marcott et al. (2013), take the view that, globally, the HCO was 0.7°C warmer than the bottom of the LIA. Such low temperature variability for the Holocene rests on tropical warming of 0.4°C during the HCO, and Southern area HCO cooling of 0.4°C.

At the core of the issue is the question: are current temperatures outside the registered bounds for Holocene temperatures? The cryosphere clearly shows that glaciers all over the world were significantly more reduced during the HCO than at present (Koch et al., 2014). The biosphere generally agrees since the extension of species such as the water chestnut and the pond turtle were then north of their present European climatic limits and the treeline has not reached its HCO maximum latitude or altitude in Sweden (Kullman, 2001), Canada (Pisaric et al., 2003), Russia (MacDonald et al., 2000), the Alps (Tinner et al., 1996), or Colombia (Thouret et al., 1996). The marine biosphere agrees as current levels of coccolithophores in the tropical oceans are lower than during the HCO (Werne et al., 2000), which is another indication that the oceans are not as warm as then.

In contrast to Marcott et al. (2013), the non-tropical Southern Hemisphere post HCO Neoglacial cooling is well documented in the many glaciers from the Southern Andes and New Zealand reviewed by Porter (2000). Their data demonstrates that Southern Hemisphere glaciers were smaller during the HCO, and that the early Neoglacial advance began between 5400-4900 BP. In southern Africa, Holmgren et al. (2003) have shown persistent Holocene cooling since 10,000 yr BP. In Antarctica Masson et al. (2000), identify an early Holocene optimum at 11,500-9,000 BP followed by a second optimum at 7,000-5,000 BP. Shevenell et al. (2011), show that the Southern Ocean has cooled by 2-4°C at several locations in the past 10-12 kyr. The Holocene cooling of just 0.4°C proposed by Marcott et al. (2013) for the Southern 30-90°S region appears to be an underestimation. At Southern latitudes, the HCO cannot be explained by precessional summer insolation changes, and large-scale reorganization of latitudinal heat transport has instead been invoked. Decreasing obliquity should also be considered a cause.

However, it is in the tropical areas where Marcott et al. (2013) becomes more controversial. The fossil coral Sr/Ca record at the Great Barrier Reef, Australia, shows that the mean SST ~ 5350 BP was 1.2°C warmer than the mean SST for the early 1990s (Gagan et al., 1998). At the Indo-Pacific Warm Pool, the warmest ocean region in the world, Stott et al. (2004) find that SST has decreased by ~ 0.5°C in the last 10,000 years, a finding confirmed by Rosenthal et al. (2013), who show a decrease of 1.5-2°C for intermediate waters. East African lakes show temperatures peaking toward the end of the HCO, followed by a general decrease of 2-3°C to the LIA (Berke et al., 2012). Tropical glaciers at Peru (Huascarán) and Tanzania (Kilimanjaro) display their highest δ18O values (warmest) at the HCO, followed by a general decline afterwards (Thompson et al., 2006). The position that the tropics have experienced warming since the HCO appear to be based, in large part, on marine alkenone proxies, however many alkenone records are from upwelling areas that have high sedimentation rates, but often display inverted temperature trends. Even worse, they generally do not agree with Mg/Ca proxies. Leduc et al. (2010) attempt to resolve the discrepancy between these two paleo-thermometry methods and note that none of the seven Mg/Ca records available for the East Equatorial Pacific have exhibited monotonous warming during the Holocene. They attribute the discrepancy with the alkenone annual temperature signal, by suggesting that it only captures the winter season and thus responds mainly to changes in insolation during that season. This explanation brings the divergent alkenone records in agreement with the rest of the marine and land tropical records that display a tropical cooling since the HCO. If we estimate this cooling in the 0.5-1°C range it is clear that Marcott et al. (2013) are underestimating global Holocene cooling and therefore HCO global temperatures.

An estimate of ~ 1.2°C global temperature decrease between average HCO temperatures and the bottom of the LIA is therefore consistent with global proxies, glaciological changes, and biological evidence. Model reconstructions (Renssen et al., 2012) also disagree with Marcott et al., 2013 since they show warming in the tropical areas during the HCO with respect to pre-industrial temperatures.

The Mid-Holocene Transition and the end of the African Humid Period

The MHT is a period of time between 6,000 and 4,500 yr BP when a global climatic shift took place at a time of significant human cultural changes that are associated with the transition from the Neolithic to the Bronze Age. The MHT separates the HCO from the Neoglacial, and is characterized by periods of global glacier advance interrupted by periods of partial recovery.

The principal cause of this global climatic shift was the redistribution of solar energy as the northern summer insolation decrease reached its maximum rate. This redistribution of solar energy, due to orbital forcing, produced a progressive southward shift of the Northern Hemisphere summer position of the Intertropical Convergence Zone (ITCZ). This accompanied a pronounced weakening of summer monsoons in Africa and Asia and increased dryness and desertification at around 30°N latitude in South America, Africa and Asia. The associated summertime cooling of the NH, combined with changing latitudinal temperature gradients in the world oceans, likely led to an increase in the amplitude of the El Niño Southern Oscillation (ENSO). The effect of these changes had world wide repercussions in temperature and precipitation patterns (figure 39).

Figure 39. Climate pattern change at the Mid-Holocene Transition. The shift from the Holocene Thermal Maximum to the Neoglacial involved a complete reorganization of the Earth’s climate, mainly directed by the southward migration of the Intertropical Convergence Zone (ITCZ) and the weakening of the African, Indian and Asian summer monsoons Source: H. Wanner & S. Brönnimann, 2012. PAGES news 20, 44-45.

The 23 kyr precession cycle is the main force behind the seasonal changes in the North-South temperature gradient that are so important for the climate in general and the precipitation regime of the ~30°N tropical band. The orbital monsoon hypothesis was first proposed by Kutzbatch (1981) and is supported by current evidence. Rossignol-Strick (1985) demonstrated that the dark organic-rich layers in the Mediterranean sediments, known as sapropels, represent periods of intense African monsoon every 23 kyr, modulated by the precession and eccentricity cycles. These sapropel formation periods also correspond to African Humid Periods, when the African monsoon produces enough precipitation over the Sahara to sustain a savanna type ecosystem. The last such period started about 15 kyr BP, but had a dry interval during the Younger Dryas at 12.5 kyr BP. As the Sahara became covered in vegetation, with large rivers and lakes, and populated by large mammals, it became inhabited by humans (figure 40). The Green Sahara entered a dryness crisis around 5.8 kyr BP and became a desert in just 500 years when the ecosystem collapsed and its human population crashed. Climate refugees from the Sahara greatly increased the population in the Nile valley and shortly after 5500 BP Egyptian society began to grow and advance rapidly towards refined civilization. Extensive use of copper became common during this time (Chalcolithic Period). The process culminated 5100 yr BP with the unification of Egypt under the first pharaoh in one of the first complex civilizations.

Figure 40. The African Humid Period. A. Climate-controlled occupation in the Eastern Sahara during the main phases of the Holocene. Red dots indicate major occupation areas; open dots indicate isolated settlements. During the Last Glacial Maximum and the terminal Pleistocene (20,000 to 12,500 BP), the Saharan desert was void of any settlement outside of the Nile valley. With the abrupt arrival of monsoon rains at 12,500 BP, the desert was replaced by savannah-like environments and became inhabited by prehistoric settlers. After 9,000 BP, human settlements became well established all over the Eastern Sahara, fostering the development of cattle pastoralism. Retreating monsoonal rains caused the onset of desiccation of the Egyptian Sahara at 6,300 BP. Prehistoric populations were forced to the Nile valley. The return of full desert conditions all over Egypt at about 5,500 BP coincided with the initial stages of pharaonic civilization in the Nile valley. Source: R. Kuper & S. Kröpelin. 2006. Science 313, 803-807. B. Dust flux (aridity proxy, red curve, inverted) record from the NW African coast 658C core related to a population proxy (black curve) based in the summed probability distribution of 3287 calibrated 14C ages from 1011 archeological sites between 14,000-2,000 years BP. Dotted lines indicate the concurrent end of the African Humid Period and population collapse. Source: K. Manning & A. Timpson. 2014. Quat. Sci. Rev. 101, 28-35.

Several authors have noticed that the MHT (6,000 to 4,500 yr BP), in addition to a global climatic pattern change, also underwent a significant change in the principal climate forcings. Debret et al. (2009) after studying 15 climate proxies from marine sediments (North Atlantic, West Africa and Antarctic), ice-core records (South America and Antarctica), cave speleothems (Ireland) and lacustrine sediments (Ecuador) by wavelet analysis, concluded that the first part of the Holocene was characterized by frequencies typical of high solar activity at 1000 years and 2500 years. The 2500 year frequency is continuous throughout the Holocene (figure 41 F). Around 5,000 years BP, the Thermohaline Circulation was finally stabilized for the second half of the Holocene (figure 41 D). MHT is a key period in the Holocene since many parameters influencing weather or climate changed abruptly. Sea level stopped increasing (figure 41 E), the flow of meltwater became insignificant, and insolation reached its maximum variation (figure 41 C). The millennial solar cycle disappeared in favor of a cyclical internal (ocean) forcing (figure 41 F).

Figure 41. Bimodal pattern of global climate during the Holocene. Global climate is dominated by a spectral imprint attributed to solar forcing (red bars) during the Holocene Thermal Maximum (HTM), and to oceanic forcing (blue bars) during the Neoglacial. (A) Glacial activity indicated by soil particles content (rAP) in Lake Blanc Huez (Alps) LBH06 core interpreted as a runoff process marker largely due to snowmelt. (B) Total Organic Carbon (TOC) values, anti-correlated to lightness (L*) fluctuations given by spectrophotometry as an indicator of glacial activity. (C) Solar energy. And (D) the North-Atlantic circulation evolution over the Holocene reflected by sea surface temperature (SST) in the North Atlantic. The light gray hatched area represents the Mid-Holocene Transition from one mode to the other. Source: S. Simonneau et al. 2014. Quat. Sci. Rev. 89, 27-43. (E) Sea Level reaches near maximum height at this time. (F) Frequency pattern based on wavelet analysis of a variety of proxies from different locations shows the first half of the Holocene dominated by frequencies attributed to solar forcing (red bars), while the second half of the Holocene sees a decrease in forcing from some solar frequencies and an increase from frequencies attributed to oceanic forcing (blue bars), together with an increase in ENSO forcing (green bar). Source: M. Debret et al. 2009. Quat. Sci. Rev., 28, 2675-2688.

Similar conclusions were reached by Simonneau et al. (2014), studying proglacial lacustrine sediments in the Alps. They show that over the last 9,700 years, the Holocene lake record has a bimodal pattern whose transition is gradual and occurred between 5,400 and 4,700 yr BP. The Early Holocene is characterized by reduced glacial activity due to increasing solar forcing and high summer insolation. After 5,400 yr BP, lacustrine sedimentation is marked by a gradual increase of minerogenic sediments and a reduction in organic content, suggesting a transition to wetter climatic conditions (figure 41 A & B). This climate change is synchronous with the gradual decrease of summer insolation and the gradual reorganization of oceanic and atmospheric circulation, characterizing the beginning of the Neoglacial period.

A bimodal climate pattern was also identified during the Holocene by Moy et al. (2002) in the Laguna Pallcacocha sediment proxy for ENSO activity for the last 12 kyr (figure 42). They found the HCO was dominated by millennial solar forcing and the Neoglacial was dominated by oceanic-atmospheric forcing. These periods were separated by the MHT. ENSO activity was essentially absent during most of the HCO and first becomes statistically significant around 7,000 yr BP, increasing considerably after 5,600 yr BP, and displaying many very strong peaks of activity during the Neoglacial period. Moy et al. also observe that periods of high North Atlantic iceberg activity, indicative of significant cooling (Bond events) tend to occur during periods of low ENSO activity immediately following a period of high ENSO activity. This suggests that some link may exist between the two systems (figure 42; Moy et al., 2002).

Figure 42. Distribution of El Niño Southern Oscillation (ENSO) activity during the Holocene. ENSO activity also displays a bimodal distribution, with low ENSO activity during the HCO and high ENSO activity during the Neoglacial. Cold Bond events, marked by increases in ice-rafted debris (inverted), tend to occur immediately following periods of high ENSO activity, and coincide with periods of low ENSO activity.

From a thermodynamic point of view high ENSO activity transfers great amounts of heat from the ocean sub-surface to the atmosphere, and afterwards a great part of that heat is radiated to space. This constitutes a cooling event from a whole Earth climate system perspective, even if it appears as warming from a lower atmosphere perspective. It is proposed that high ENSO activity is made possible by a high equator-to-pole temperature gradient. During the HCO the temperature gradient was kept low by high polar insolation due to high obliquity. After 7,000 yr BP the decrease in polar insolation and the increase in tropical insolation favored a progressive increase in the gradient, especially during prolonged periods without significant cooling, i.e. immediately preceding a Bond event. The profound cooling from a Bond event would eliminate or greatly reduce ENSO activity by quenching the thermal energy required for an El Niño event. If correct, high ENSO activity would be a sign of a cooling planet.

Conclusions

1) The Holocene is a period of 11,700 years characterized by an intense warming for about 2,000 years and a progressively accelerating cooling for the last 6,000 years, following the changes in obliquity of the Earth’s axis.

2) Fluctuations in greenhouse gases cannot explain Holocene climatic changes and, indeed, their concentration changes run opposite to temperature trends for most of the Holocene.

3) Climate models perform very poorly when trying to reproduce Holocene climate evolution. This is likely due to having too much sensitivity to changes in greenhouse gases and too little sensitivity to insolation and solar variability.

4) The Holocene Climatic Optimum was a more humid period, 1-2°C warmer than the Little Ice Age, during which global glaciers reached their minimum extent.

5) The Mid-Holocene Transition, caused by orbital changes, brought a complete change in climatic mode, with a decrease in solar forcing and an increase in oceanic forcing, displacing the climatic equator and ending the African Humid Period, while increasing ENSO activity.

Acknowledgements

I thank Andy May for reading the manuscript and improving its English.

That all looks reasonable over long time periods but does not seem to adequately explain the solar induced millennial climate cycling from MWP to LIA to the present warm period
It is the latter which has given rise to current concerns.

from the nerc link:
“The Atlantic overturning circulation is declining and the AMO is moving to a negative phase.”

It would appear that a slowing of the AMOC drove the AMO warming since 1995. Also at the seasonal noise level on the RAPID data, low MOC events occur during negative NAO episodes AND concurrently with warm pulses to the AMO.

Robert, the Smeed paper suggests the cold winter of 2009-2010 was driven by cold SST’s in the North Atlantic. The first problem with is that the SST’s were not particularly cold. The second larger problem is a cause and effect logic issue, the MOC rates are NAO driven, so we have to look for another driver of the NAO variability causing the cold winter episodes. My solar based NAO forecasts captured the cold Jan-Feb 2010, and cold from the last week of Nov and through Dec.

Smeed et al:
“Cunningham et al. (2013)suggested that this reduction was the major contributor to
low wintertime sea-surface temperatures in the region be-
tween 26◦N and 41◦N. The downturn of 2009–2010 was
followed by an anomalously cold winter in NW Europe with
strong negative North Atlantic oscillation (NAO) in Decem-
ber 2010. Maidens et al. (2013) noted that the anomalous
conditions were predicted by long-range forecasts several
months in advance. Using an ensemble of hindcasts, Maid-
ens et al. (2013) concluded that the factor that led to the pre-
dictability of this winter was the anomalous upper-ocean heat
content and SST. This suggests that the monitoring AMOC
at 26◦N can provide valuable information for seasonal prediction”

“It has been observed that several multi-secular climatic and oceanic
records present large cycles with periods of about 50-70 years with an average of 60 years… This sequence has been filtered of its fast fluctuations (by applying a six year moving average smooth algorithm) and it has been plotted against itself with a time-lag of about 60 years. The figure clearly suggests the existence of an almost perfect cyclical correspondence between the periods 1880-1940 and 1940-2000. The peak in 1880 repeats in 1940 and again in 2000. The smaller peak in 1900 repeats in 1960. This 60-odd year oscillation cannot be associated with any known anthropogenic phenomenon.” ~N. Scafetta

As has been pointed out global glaciers reached their peak during the LIA.

Glacial activity was relatively low during the warm roman period and mining was carried out at high altitudes in the alps. They got covered by subsequent glacial advances and then in recent decades have been revealed again.

It is hardly surprising that the peak glacial advances which ended several hundred years ago should then melt as the climate warmed. These glaciers had not been at their extended peak for ever, they grew to that size in recent centuries during the little intermittent ice age and then have receded.

I have a very nice chart for Part B that Olga Solomina sent me about glacier advances during the Holocene, to illustrate the Neoglacial period.

I think that the interesting question is if global glacier melting over the past 200 years up to now is consistent with what should be considered normal for this time of the Neoglacial. Most experts seem to think that the answer to that is negative.

We used to have a commentator here called Max Anacker who lived in Switzerland and was an engineer. He was especially interested in Roman mines, especially silver ones. I visited him and we did some work together on this subject and I physically went to examine several glaciers.

The evidence is that Glaciers largely disappeared around the Roman period (or became much less extensive-see article ‘Green Alps’.) There is a theory that Hanibal crossed the alps easier than was imagined during Victorian times due to the lack of glacial ice in most seasons/years.

Prof Hunt used to run expeditions to find the likely passes he used and again after examining these physically it appears likely that snow/glaciers then were not as widespread as today. These are backed up by tree growing at various elevations. The otzi traveller is also interesting and again I have been to Bolzano to examine the evidence

The mines gradually disappeared under ice during the dark ages and reappeared at times as the climate warmed again (see E Roy Ladurie ‘Times of feast times of Famine.) Again I have examined those and been to various museums in such places as Zermatt and Chamonix to examine the records.

The Roman sites were smothered during the intermittent little ice age but again have reappeared as the climate has warmed. So the evidence is that it is normal for this to occur

Bearing in mind that the little Ice age appears to have been an extreme anomaly during the Holocene, it is surely not surprising that they should melt at the rates we currently see as the temperatures roughly reassert themselves.

I have nothing personal to add to that debate, only from reading the literature. Glaciers are complex proxies very much like tree rings. There are always glaciers somewhere going the opposite way to most glaciers. The evidence appears to support that they depend more on winter precipitations than on summer temperatures, but when considered globally then winter precipitations are more or less averaged and summer temperatures become more important. Other factors that affect interpretation are if glaciers end in land or sea, and their slope, as glaciers with higher slope behave differently than glaciers with lower slope.

It is important then to considerer glaciers as globally as possible. For example Swiss Alps advances and Austrian Alps advances receive different names and do not always coincide.

The Roman period glacier retreat is vey clear. This was a very long period without significant grand solar minima of almost 1000 years between 2600-1700 yr BP that can be seen in the Bond series as not having any significant cooling event. It really stands out as the longest period without cooling events in the entire Holocene, and I will discuss the reasons for that when I review the millennial solar cycle. The consequence is that it produced the largest glacier retreat of the Neoglacial until the modern retreat. It was also an out of trend retreat.

I have added the trend lines, and as you can see there is no discussion that like during the Roman period, the current retreat is also abnormal when considering Neoglacial trends. We know the cause of the Roman out-of-trend retreat, a very long warm period. What is the cause of the present out-of-trend retreat? This warm period has not been very long. It’s been warm only from the 1920s warming, and glaciers are retreating since about 1850, a mere 170 years.

Compared to that question, the question of which period has seen a more profound retreat is secondary. Even with the same retreat this period would be more abnormal, as it is 2000 years later in the Neoglacial. And experts seem to think that current retreat has exceeded somewhat the Roman retreat.

The evidence appears clear. That is why very few glaciologists think that the current retreat is usual. And I agree with them. Whatever we think of current global warming and the effect of CO2, glaciers are behaving unusually for what it should be expected from them at this time.

it snows more in warm times and it gets cold after. it snows less in cold times and it gets warm after. They ignore the really wonderful ice core data that documents this. They consider ice extent a result of other forceings. The ice extent is the primary forcing. they do not understand, they do not even have a clue. Look at my presentation and tell me what you think about it. Help prove me right or wrong. If I am wrong, I will search for what is right. If you think I am right, please promote it.http://popesclimatetheory.com/

I do think that you are right that snow levels are probably neglected as a climatic factor, and that it is interesting that snowing is not responding to global warming as anticipated by alarmist scientists. Snow is one of the feedbacks that is not understood, and this year record snow increase in Greenland, just after “the latest warmest year,” shows it.

However I think you have built yourself a non-falsifiable hypothesis. If a factor causes warming, like Milankovitch obliquity changes, then you will say that what it does is to decrease snowing and the ice reduction does the warming. You are trapped in the dilemma of distinguishing between cause and effect. The same problem as Ralph Ellis with his dust glacial control hypothesis. Usually people without a good training on the scientific method get tangled into non-falsifiable/cause-effect hypothesis, because when you build a hypothesis you have to try to tear it apart yourself and make sure that there are ways to demonstrate that it is false. Otherwise it is not a hypothesis, but a belief system.

Most people are likely to think that climate is a very complex thing that cannot be explained except as a combination of many factors some more important that others, and therefore not be inclined to subscribe to hypothesis that rely on an overriding factor, be it CO2 or ice.

“Cold events see an increase in negative NAO which is directly associated with increased El Nino.”

Figure 42, from Moy et al., 2002, and the authors in the article defend that Bond cold events during the Holocene were not associated with increased El Niño. To me it would be easier to explain that El Niño is always associated with cooling, but that is not what the evidence shows.

“Deeper glacial periods see near permanent El Nino conditions.”

That is interesting. Do you have bibliography to support it? I only have info on El Niño during the Holocene. It makes sense as El Niño was suppressed during the HCO.

The general increase in El Nino in the last 6 kyr in fig 42 would suggest a decline in climate forcing. The detail though does not agree with other El Nino proxy records I have seen.
Recent solar minima saw an increase in El Nino, roughly a doubling in frequency in the colder part of the Dalton Minimum 1807-1817.

One other interesting thing is that the forcing change we get each decade now is the same as over the entire 5000 years when CO2 increased from 260 to 280 ppm, so no wonder we see the temperature rising so fast now, because the forcing rate of change is a few hundred times faster. In the past the temperature rate of change was -0.1 C per thousand years, or -0.001 C per decade, while now it is near 0.2 C per decade. Orbital changes significantly amplified by albedo feedbacks likely dominated the period since the HCO, but in the last century forcing changes have rapidly accelerated as has the coincident temperature rate of change.

Jim D “In the past the temperature rate of change was -0.1 C per thousand years, or -0.001 C per decade, while now it is near 0.2 C per decade.”
Jim, the temperature change per year is much greater either way than decadal or millennial comment .
Does that give you any idea of why your comment is wrong?
0.1C per thousand
0.001C per decade
0.0001C per year according to your ….. logic.
Sorry.

Explain one thing. Why does the temperature change per year matter for climate? You should be looking at 30 year changes, and ideally centuries. When looking at a 1 C change over a century that is, by anyone’s definition, a climate change. Not only that, but a hundred times faster than the change due to orbital forcing while the forcing change is also that much faster.

Climate change is not a question of logic, but of evidence. The Holocene climate history actually doesn’t support a high sensitivity, as CO2 changes and temperature changes went the opposite way almost all of it. This proves other factors were more important.

“Holocene climate history actually doesn’t support a high sensitivity, as CO2 changes and temperature changes went the opposite way almost all of it.”
That doesn’t follow. CO2 changed in the range from 260 to 280 ppm, in your graph. There could be very high sensitivity and you still wouldn’t notice the temperature change against the other effects.

“That doesn’t follow. CO2 changed in the range from 260 to 280 ppm, in your graph. There could be very high sensitivity and you still wouldn’t notice the temperature change against the other effects.”

It decreased from 267 to 258 ppm between 10,000 and 6,800 yr BP, when temperatures were not falling, and it increased from 258 to 283 ppm by 600 yr BP, when temperatures where falling.

If there was a very high sensitivity temperatures could not go against CO2 changes. In fact already the three climate models used by Liu et al., 2014 that have a sensitivity of ~ 3 already produce warming instead of reproducing the actual cooling under those conditions. A clear indication that climate sensitivity is probably significantly lower than 3.

The word “support” seems to indicate some logic going on, Javier. You used that word a few times already. Your own reasoning shows that evidence doesn’t stand alone. So your claim that climate science is not a matter of logic may be a tad too strong.

Also, “support” sometimes indicate weasel wording. But that’ll be for another time.

“If there was a very high sensitivity temperatures could not go against CO2 changes.”
257 to 283 ppm (both being transient extremes) corresponds to 0.13 doublings. At ECS 3, that is about 0.4°C, assuming equilibrium reached, and ignoring the effect of earlier and later changes. That’s an absolutely max case. According to Marcotte the temperature dropped by about 1°; your ice core record says about 2°. There is no reason why the sensitivity to obliquity could not have been a little higher, part-offset by the small CO2 change.

> [S]cience matters are usually settled by empirical evidence, not by clever use of the language.

Science matters are settled by scientists who don’t hide their *arguments* behind their evidence basis and dance around other people’s *reasoning* with slogans about evidence, Javier. That your two latest ones are false don’t help either, but that’s just a bonus.

Nick. Shakur is currently looking at reconstructions for this period as they don’t put too much faith in current work.
See the holocene conumdrum. For real working scientists the issue is active and uncertain.

Modern hydrology places nearly all its emphasis on science-as-knowledge, the hypotheses of which are increasingly expressed as physical models, whose predictions are tested by correspondence to quantitative data sets. Though arguably appropriate for applications of theory to engineering and applied science, the associated emphases on truth and degrees of certainty are not optimal for the productive and creative processes that facilitate the fundamental advancement of science as a process of discovery. The latter requires an investigative approach, where the goal is uberty, a kind of fruitfulness of inquiry, in which the abductive mode of inference adds to the much more commonly acknowledged modes of deduction and induction. The resulting world-directed approach to hydrology provides a valuable complement to the prevailing hypothesis- (theory-) directed paradigm.

In hydrology a limited set of physical processes are relatively easy to represent numerically – and models are calibrated against data. If they become unstable – it is a matter of reducing the size of cells or the calculation time step.

In climate – there are hundreds if not thousands of relevant processes most of which are inadequately understood or not at all. And climate models are always unstable. The best use for models are for hypothesis testing for physical processes and interactions. But – ultimately – all models require calibration.

The more fruitful approach is the use of abductive inference – inference which starts with an observation and then applies the simplest and most likely explanation. It is the opposite of deductive logic – or a narrative based on physical reasoning –
which is what rules the blogosphere. Wee willie lacks even a modest understanding of physical law and relies entirely on undergraduate level sophistry. It is not even all that clever or amusing.

There are two aspects to a science of uberty. It is inherently uncertain Have you chosen the right data sets? Do the right sets exist at all and with sufficient accuracy? Are there alternative inferences? It must all be couched in may, perhaps, on the balance of probabilities, all things being equal, etc. Essential ‘weasal words’. The temptation to claims of precision or certainty should be resisted. Especially with paleodata.

The second problem is how it can be tested? How is it science at all?

But the answer to the question is that there was a reduction of about 25W/m2 in reflected shortwave between the last glacial maximum and preindustrial – and an increase of some 2W/m2 CO2 forcing. The sensitivity to forcing is about 0.2K/W/m2 – or 0.7K for a CO2 doubling forcing.

“257 to 283 ppm (both being transient extremes) corresponds to 0.13 doublings. At ECS 3, that is about 0.4°C, assuming equilibrium reached, and ignoring the effect of earlier and later changes. That’s an absolutely max case.”

CO2 changed from 190 ppm to 265 ppm during deglaciation, an increase of 75 ppm which corresponds to 0.39 doublings. At ECS 3, that is about 1.2°C. However the estimated change in average global temperature was ~ 4-5°C. Your absolute max case says CO2 played a very small role in deglaciation. Whichever way you look at it, the evidence says CO2 cannot have played a big role in past temperature changes.

However what Liu et al., 2014 have demonstrated is that climate models believe the last 8000 years the world should have been warming. Why? GHGs were rising, but northern summer insolation was decreasing, polar insolation was decreasing. The increase in southern summer insolation was small. Models tuned to what we think is presently happening do not perform over past conditions. If climate sensitivity was higher than 3, models would perform even worse, and if it was smaller they would perform better. Clearly defending a high climate sensitivity makes the Holocene Conundrum a worse problem.

I don’t think anyone ever claimed that CO2 played a large role in the Ice Ages. Milankovitch has always been the explanation as far as I know. CO2 only provided a positive feedback. Since the Ice Ages, we have only had half a doubling and a 5 C temperature rise, so if you assigned the warming to CO2, the sensitivity would have to be 10 C per doubling.

> more fruitful approach is the use of abductive inference – inference which starts with an observation and then applies the simplest and most likely explanation. It is the opposite of deductive logic – or a narrative based on physical reasoning

Chief restricts the concept of logic to deductive logic, rediscovers Inference to the best explanation I’ve been promoting on this blog since at least 2010, and thus wins again. Tough to stop the Chief. Not even emphasizing *arguments* and *reasoning* would.

Most if not all ampliative logics (or non-monotonic logics in general) include mundane stuff like an inference rule and the law of contradiction.

“Thus, the CO2 changes may amplify a warming already in progress around ice volume terminations but are unlikely to be the source of the climate change, because they are decoupled during prominent intervals such as MIS 1 and 5d. ”

The major cause of albedo change – from 0.37 (approximately) to 0.30 (give or take) was ice sheet extent on northern land masses.
It is aout a 25W/m2 change.

“Chief restricts the concept of logic to deductive logic, rediscovers Inference to the best explanation I’ve been promoting on this blog since at least 2010, and thus wins again. Tough to stop the Chief. Not even emphasizing *arguments* and *reasoning* would.”

Does wee willie imagine this is English?

“Abductive reasoning (also called abduction, abductive inference, or retroduction) is a form of logical inference which starts with an observation then seeks to find the simplest and most likely explanation. In abductive reasoning, unlike in deductive reasoning, the premises do not guarantee the conclusion.” Starting from observation is the important point in this uberty model of science.

> Starting from observation is the important point in this uberty model of science.

Thus Chief wins again, this time by touting an idea that is at least as old as Aristotle, His win comes at the expense of forgetting Javier’s wonderful but oversimplistic climate change is not a question of logic, but of evidence.

Cecil Terwilliger (brother to Sideshow Bob) was Springfield’s Chief Hydrological and Hydrodynamical Engineer. He opined that this was a sacred vocation in some cultures. The more I thought about this the more it resonated with me. I am an hydrologist by training, profession and (much more) through a deep fascination with water in all its power and beauty. Given the importance of water to us practically and symbolically, there is more than an element of the sacred.

I lightheartedly adopted the handle of Chief Hydrologist. But it became the object of far too many internet trolls as self aggrandizement, a pretense to authority, a sock puppet – whatever. It just all got far too tedious to persist.

But wee willie still persists in using a quite innocent nom de plume to not so subtly ridicule – linked to a frequent and intrusive disparagement to do with winning of all things. It is all word games with zilch science content and a large element of derision. It all says more about wee willie.

And as I pointed out – abductive inference in modern science has nothing in common with Aristotles deductive logic. There is no sense in which it proceeds from premises to an unavoidable conclusion. It proceeds from observation to a parsimonious explanation and is fraught with uncertainties. It differs from the usual notion of empirical science in which and experiment is devised to test a hypothesis. But it is the essence of modern natural sciences – and climate is a germane example when it is not pretending that models are an experiment.

The Holocene climate history actually doesn’t support a high sensitivity

I haven’t suggested that. I’m talking about the support for high sensitivity due to reconstructed LGM temperature. The high-variability Holocene climate history you’ve proposed would necessarily mean a high-end LGM-preindustrial temperature difference, in the region of 8K (because the proxies you’ve highlighted showing higher Holocene variability also show larger LGM-preindustrial difference). CO2 and other greenhouse gases very much do change in line with temperature changes here, along with ice sheets and other factors.

Many ECS estimates have been published using LGM-preindustrial temperature difference, and mostly considered a change of around 5K. The evidential corollary of your Holocene history is that all those studies were significant underestimates.

> And as I pointed out – abductive inference in modern science has nothing in common with Aristotles deductive logic.

And as I pointed out, this is false: non-monotonic logics can still manage some of the stuff classical logics do. They are logics, and are still bound by the law of non-contradiction. Even if we accept that scientists use abductive reasoning to form hypotheses, they still apply the law of identity to distinguish them. Scientists still work by assuming that facts are either true or false, never both or something in between. It’s really hard to let go of the laws of thoughts known since Plato.

I could also point out that Chief’s laius is relevant here because he’s trying to counter the idea that science works by deduction, e.g. by Modus Tollens like Popper held. But this is a strawman – nobody pledges for falsificationism here. Chief simply got carried away because I dared to underline that empirical science still has a logical component. And now that I said the Philosopher’s name, he connects to his theory of syllogisms instead of his empirical work:

Reasoning from observations has been important to scientific practice at least since the time of Aristotle who mentions a number of sources of observational evidence including animal dissection (Aristotle(a) 763a/30–b/15, Aristotle(b) 511b/20–25).

That’s clearly not the case, because most of the proxies that I have discussed do not extend into the glacial period. You are trying to argue an issue for which the presented evidence is not adequate.

“Many ECS estimates have been published using LGM-preindustrial temperature difference, and mostly considered a change of around 5K. The evidential corollary of your Holocene history is that all those studies were significant underestimates.”

That’s clearly not the corollary. Most of the studies on deglaciation temperature changes do not extend to the LIA. They try to measure temperature changes between LGM and HCO, established at 4-5°K. I think that our current understanding is quite consistent. ~ 4-5°K increase from LGM to HCO, ~ 1-2°K decrease from HCO to LIA, and ~ 0.8-1°K increase from LIA to 21st century.

Poor wee willie bizarrely countered that I had stolen the idea of logic from Aristotle. I said that Aristotle’s logic proceeds from premises to an inevitable conclusion – whereas abductive inference proceeds from observation to a plausible conclusion in which imagination is the key rather than logic.

Einstein is writing to mathematician Jacques Hadamard, wrote that “[t]he words of the language, as they are written or spoken, do not seem to play any role in my mechanism of thought. The psychical entities which seem to serve as elements in thought are certain signs and more or less clear images which can be ‘voluntarily’ reproduced and combined…. The above mentioned elements are, in my case of visual and some of a muscular type…. Conventional words or other signs [presumably mathematical ones] have to be sought for laboriously only in a secondary stage, when the associative play already referred to is sufficiently established and can be reproduced at will”https://www.psychologytoday.com/blog/imagine/201003/einstein-creative-thinking-music-and-the-intuitive-art-scientific-imagination

Willie responded that Aristotle cut up dogs – thus providing an unbroken link from Aristotle’s teleology, to scientific empiricism and abductive inference. Because – and I paraphrase only slightly – they all use logic. Which – btw – I stole from Aristotle and pretended it was something new I had discovered.

I am more inclined to ascribe Holocene changes to changes in solar activity than the slow changes from orbital eccentricities.

In this you can see the mid-Holocene transition – reflected in a transition from La Nina dominance to El Nino dominance some 5,000 years BP in the Moys et al 2002 record – that dried the Sahel.

There are 2000 and 1000 year periodicities. Just 3,500 years ago there were a long series of El Niño with red intensity greater than 200 and civilisations fell. For comparison – red intensity in the ‘monster’ 1997/1998 El Niño event was 99.

The 1000 year record of ENSO from the Law Dome in Antarctica mirrors the 1000 year cosmogenic isotope record.

“ENSO causes climate extremes across and beyond the Pacific basin; however, evidence of ENSO at high southern latitudes is generally restricted to the South Pacific and West Antarctica. Here, the authors report a statistically significant link between ENSO and sea salt deposition during summer from the Law Dome (LD) ice core in East Antarctica. ENSO-related atmospheric anomalies from the central-western equatorial Pacific (CWEP) propagate to the South Pacific and the circumpolar high latitudes. These anomalies modulate high-latitude zonal winds, with El Niño (La Niña) conditions causing reduced (enhanced) zonal wind speeds and subsequent reduced (enhanced) summer sea salt deposition at LD. Over the last 1010 yr, the LD summer sea salt (LDSSS) record has exhibited two below-average (El Niño–like) epochs, 1000–1260 ad and 1920–2009 ad, and a longer above-average (La Niña–like) epoch from 1260 to 1860 ad. Spectral analysis shows the below-average epochs are associated with enhanced ENSO-like variability around 2–5 yr, while the above-average epoch is associated more with variability around 6–7 yr. The LDSSS record is also significantly correlated with annual rainfall in eastern mainland Australia. While the correlation displays decadal-scale variability similar to changes in the interdecadal Pacific oscillation (IPO), the LDSSS record suggests rainfall in the modern instrumental era (1910–2009 ad) is below the long-term average. In addition, recent rainfall declines in some regions of eastern and southeastern Australia appear to be mirrored by a downward trend in the LDSSS record, suggesting current rainfall regimes are unusual though not unknown over the last millennium.” Vance et al 2013 – A Millennial Proxy Record of ENSO and Eastern Australian Rainfall from the Law Dome Ice Core, East Antarctica

More salt is La Nina. A solar influence explains both broad and fine scale variability – 20 to 30 year regimes, the change in the ENSO beat in the early 20th century, the mid Holocene transition, cool and warm periods in the last millennia. It explains these far better than slow orbital eccentricity changes. A mechanism is helpful.

The figure shows global “wind and gyre circulation changes hypothesized to be associated with multidecadal (a) warm and (b) cool phases of the North and South Hemispheres. White arrows indicate regions of enhanced wind and black arrows indicate areas of enhanced gyre circulation. The blue patches indicate the sinking waters in the North Atlantic. The zonal warm phase occurred from the 1910s to 1940s and 1970s to 1990s and is characteristic of strong westerly winds in the northern and southern hemisphere. North Pacific and North Atlantic subarctic gyre circulations enhance with sinking waters associated with the northern North Atlantic winter. In the Atlantic subtropical gyre circulations also enhance. Some surface waters travel from the Indian Ocean to the south Atlantic and join the Gulf Stream in the North Atlantic. The meridional cool phase occurring from the 1940s to 1970s and 1990s to present consists of equatorward winds over the continents and poleward winds over the subarctic and sub-antarctic oceans, resulting as Rossby wave formations. Intensified circulation in subtropical gyre systems enhances upwelling and productivity in the California and Peru systems. Strengthened easterly trade winds increase equatorial current circulation in the Pacific. The background global chlorophyll is from Yoder et al.”

The mechanism involves solar UV/ozones chemistry. “A number of studies have indicated that the decreases in global mean temperature associated with a future decline in solar activity are likely to be relatively small3,4,5,6,7. However, variability in ultraviolet solar irradiance has been linked to changes in surface pressure that resemble the Arctic and North Atlantic Oscillations (AO/NAO)8,9,10 and studies of both the 11-year solar cycle11,12 and centennial timescales13 suggest the potential for larger regional effects. The mechanism for these changes is via a stratospheric pathway, a so-called ‘top-down’ mechanism, and involves altered heating of the stratosphere by solar ultraviolet irradiance.” Inseson et al 2015 – Regional climate impacts of a possible future grand solar minimum

Enhanced upwelling is the origin of ENSO giving rise to the notion of a La Nina ‘normal’. Trade winds spin up as a feedback and piles warm water against Australia and Indonesia. Sometimes the winds falter and warm water flows back eastward suppressing cold upwelling. The whole is a complex and dynamic system triggered by changes in atmospheric pressure zones at both the north and south poles. Mass movements of the atmospheric are driven by a marginal change in solar activity. A large reaction from a small jolt as expected with technically chaotic (abruptly changing) systems.

Solar variability is responsible for a great part of the millennial scale climate variability. But this article deals only with the background multi-millennial climate change. Solar variability cannot explain why there was a Holocene Climatic Optimum, the Mid-Holocene Transition, or the Neoglacial. Temperatures on earth respond primarily to orbital changes, that determined when the interglacial started and will determine when it will end.

There was a mid-holocene transition from low to high solar intensity that triggered a shift from La Nina to El Nino dominance. This is the proximate cause of Sahel drying.

This however would suggest cooler conditions earlier and warmer later – a paradox I would put down to slow ice and snow changes in the NH. It is not one or the other. But solar activity explains better the immense and abrupt Holocene variability at all scales.

“There was a mid-holocene transition from low to high solar intensity that triggered a shift from La Nina to El Nino dominance. This is the proximate cause of Sahel drying.”

Didn’t have anything to do with the intensity of the sun. Summer insolation displaced southward, and so did the summer ITCZ and summer monsoon. This is very well known, as it happens following the precession cycle and leaves the sapropels as records. I wonder if you read the article.

Only in the 30°N tropical band due to the drying and cloud reduction, The rest of the planet started to cool in response to falling obliquity and an increase in the Equator-to-Pole temperature gradient.

Mixed the italics and triggered moderation. Let’s try to fix the italics.

Didn’t have anything to do with the intensity of the sun. Summer insolation displaced southward, and so did the summer ITCZ and summer monsoon. This is very well known, as it happens following the precession cycle and leaves the sapropels as records. I wonder if you read the article.

I in fact read very little of the article. Enough to know that I fundamentally disagreed – as I have before with you as I recall. I did note your assumption that a shift in the ITCZ fundamentally and abruptly shifted ENSO dynamics.

There is an article I quoted suggesting the ITCZ moves towards the warmer hemisphere. I suggested that the warming from obliquity was relatively minor – certainly less than annual changes. It is an order of magnitude thing – and you suggest the ITCZ caused the mid-holocene shift of ENSO to El Nino dominance without a mechanism and nothing but a coincidence of timing it seems.

The cause I believe is solar UV/oxone chemistry modulating the northern and southern annular modes.

You may not agree – but I have a testable hypothesis. The next global climate shift – due in a 2018-2028 window – will be to yet cooler conditions.

Only in the 30°N tropical band due to the drying and cloud reduction, The rest of the planet started to cool in response to falling obliquity and an increase in the Equator-to-Pole temperature gradient.

You need top demonstrate some scientific basis for this for me to take it seriously and not just all too convenient narrative.

The Pacific state causes change in cloud anti-correlated to sea surface temperatures. e.g.

But the temperature, hydrological and biological effects are global.

The net change in planetary insolation from obliquity is zilch – what is lost in the NH is gained in the south. But there may be relevant, slow snow and ice feedbacks on NH land masses. As I said before – they are not mutually exclusive.

“I in fact read very little of the article. Enough to know that I fundamentally disagreed – as I have before with you as I recall. I did note your assumption that a shift in the ITCZ fundamentally and abruptly shifted ENSO dynamics.”

What I thought. Hard to adequately represent what I say without reading it first. You could not have noted my assumption that a shift in the ITCZ fundamentally and abruptly shifted ENSO dynamics, because that is not what I think or what I have read on the issue or what the evidence shows. I have no idea if there is any causal relationship between the position of the ITCZ and ENSO dynamics. What I know is that both changed during the MHT.

“The net change in planetary insolation from obliquity is zilch”

And the planetary insolation amount and distribution difference between the Last Glacial Maximum and now is also zilch. That means nothing. That doesn’t mean that differences due to obliquity changes are not overruling in determining the long term climatic state. I have an advantage. Temperatures on the planet do follow obliquity with about a 6500 year lag. Figure 35.

The associated summertime cooling of the NH, combined with changing latitudinal temperature gradients in the world oceans, likely led to an increase in the amplitude of the El Niño Southern Oscillation (ENSO). The effect of these changes had world wide repercussions in temperature and precipitation patterns.

And the planetary insolation amount and distribution difference between the Last Glacial Maximum and now is also zilch. That means nothing. That doesn’t mean that differences due to obliquity changes are not overruling in determining the long term climatic state. I have an advantage. Temperatures on the planet do follow obliquity with about a 6500 year lag. Figure 35.

The albedo changes from the glacial maximum are quite significant of course. Energy changes from obliquity are zilch. It is energy alone that warms and cools the planet as energy is gained or lost. So you need to posit slow changes in ice sheets. A 6500 year temperature lag from a net zero change in planetary insolation? Nonsense.

Exactly. “Changing latitudinal temperature gradients in the world oceans.” Not something that should be ignored.

“Energy changes from obliquity are zilch. It is energy alone that warms and cools the planet as energy is gained or lost. So you need to posit slow changes in ice sheets. A 6500 year temperature lag from a net zero change in planetary insolation? Nonsense.”

The data shows clearly that temperatures on the planet respond primarily to the 41 kyr obliquity cycle. If that doesn’t make sense to you that is your problem. I have already provided bibliography that you should read.

There was around a doubling of the mean El Nino frequency 1807-1817 in the Dalton Minimum, with an absence of aurora sightings in most of those years. At an event level in the space age, we regularly see slow solar wind periods associated with El Nino conditions/episodes, and faster solar wind periods with La Nina conditions/episodes.

“A number of studies have indicated that the decreases in global mean temperature associated with a future decline in solar activity are likely to be relatively small3,4,5,6,7. However, variability in ultraviolet solar irradiance has been linked to changes in surface pressure that resemble the Arctic and North Atlantic Oscillations (AO/NAO)8,9,10 and studies of both the 11-year solar cycle11,12 and centennial timescales13 suggest the potential for larger regional effects. The mechanism for these changes is via a stratospheric pathway, a so-called ‘top-down’ mechanism, and involves altered heating of the stratosphere by solar ultraviolet irradiance.” Regional climate impacts of a possible future grand solar minimum – Sarah Ineson, Amanda C. Maycock, Lesley J. Gray, Adam A. Scaife, Nick J. Dunstone, Jerald W. Harder, Jeff R. Knight, Mike Lockwood, James C. Manners & Richard A. Wood

We have low solar activity and a more negative AO. It changes winds and currents in the NH.

Changed winds and current in a negative AO enhance upwelling in the eastern Pacific – which is the origin of ENSO.

The figure shows global “wind and gyre circulation changes hypothesized to be associated with multidecadal (a) warm and (b) cool phases of the North and South Hemispheres. White arrows indicate regions of enhanced wind and black arrows indicate areas of enhanced gyre circulation. The blue patches indicate the sinking waters in the North Atlantic. The zonal warm phase occurred from the 1910s to 1940s and 1970s to 1990s and is characteristic of strong westerly winds in the northern and southern hemisphere. North Pacific and North Atlantic subarctic gyre circulations enhance with sinking waters associated with the northern North Atlantic winter. In the Atlantic subtropical gyre circulations also enhance. Some surface waters travel from the Indian Ocean to the south Atlantic and join the Gulf Stream in the North Atlantic. The meridional cool phase occurring from the 1940s to 1970s and 1990s to present consists of equatorward winds over the continents and poleward winds over the subarctic and sub-antarctic oceans, resulting as Rossby wave formations. Intensified circulation in subtropical gyre systems enhances upwelling and productivity in the California and Peru systems. Strengthened easterly trade winds increase equatorial current circulation in the Pacific. The background global chlorophyll is from Yoder et al.”

And we see increased El Nino frequency and intensity in the 20th century – as well as behaviour that mirrors solar variability over a millennia. More salt in a Law Dome ice core is La Nina.

Thus there is both mechanism and observation. I think I will disagree until something different turns up.

Several figures in this article stitch together modern climate measurements for temperature and carbon dioxide concentration with paleo-data from ice cores and other proxies. There are no current records from ice cores, and the modern surface or satellite records represent completely different sampling and measurement techniques. No on knows how to compare the current 410 ppm CO2 in clean dry air at Mona Loa with 285 ppm CO2 from Greenland or Antarctic ice core samples diffused and compressed for at least a century. The statistical stitching gives a misleading impression of extreme changes in these variables in recent times.

1) The Holocene is a period of 11,700 years characterized by an intense warming for about 2,000 years and a progressively accelerating cooling for the last 6,000 years, following the changes in obliquity of the Earth’s axis.

2) Fluctuations in greenhouse gases cannot explain Holocene climatic changes and, indeed, their concentration changes run opposite to temperature trends for most of the Holocene.

3) Climate models perform very poorly when trying to reproduce Holocene climate evolution. This is likely due to having too much sensitivity to changes in greenhouse gases and too little sensitivity to insolation and solar variability.

4) The Holocene Climatic Optimum was a more humid period, 1-2°C warmer than the Little Ice Age, during which global glaciers reached their minimum extent.

5) The Mid-Holocene Transition, caused by orbital changes, brought a complete change in climatic mode, with a decrease in solar forcing and an increase in oceanic forcing, displacing the climatic equator and ending the African Humid Period, while increasing ENSO activity.

I refer to the temperature reconstruction in figure 37 from Marcotte, et al., 2013. You correctly acknowledge the artificially enhanced terminal spike in the notes. Is that a statistical aberration or because of differences in source data? Your article is excellent and much appreciated.

The problem in Marcott et al., 2013 terminal spike came from a wrong statistical approach, as they themselves recognized later. There is a very clear post-LIA warming in the proxy data, but their effect was exaggerated by an statistical artifact due to proxy drop out, as many proxies do not extend to the end of the analysis and the average is artificially raised for the ones that do. The black curve corrects for that statistical artifact. But there is no instrumental data in Marcot et al., 2013 reconstruction. Whether right or wrong it comes from proxy data.

We have a maximum impact of orbital ecentricities at 65N balanced by changes at 65S.

“Rainfall on Earth is most intense in the intertropical convergence zone (ITCZ), a narrow belt of clouds centred on average around six degrees north of the Equator. The mean position of the ITCZ north of the Equator arises primarily because the Atlantic Ocean transports energy northward across the Equator, rendering the Northern Hemisphere warmer than the Southern Hemisphere. On seasonal and longer timescales, the ITCZ migrates, typically towards a warming hemisphere but with exceptions, such as during El Niño events. An emerging framework links the ITCZ to the atmospheric energy balance and may account for ITCZ variations on timescales from years to geological epochs.” https://www.nature.com/nature/journal/v513/n7516/full/nature13636.html

So the orbital changes may impact the mean location of the ITCZ (pronounced itch) – but where is the mechanism connecting this to ENSO dynamics?

“We have a maximum impact of orbital ecentricities at 65N balanced by changes at 65S.”

On the contrary. That figure shows very clearly that temperatures are responding mainly to obliquity. At 30 kyr BP and at 10 kyr BP 65N and 65S insolation curves were almost identical while temperatures were in absolute opposite states. The obliquity however changed in that time from minimal to maximal.

I’m crushed – here I was thinking that obliquity was an orbital eccentricity. You do realise how small insolation changes are relatively – that they balance out in an energy sense globally – and that it’s the ice and snow response on northern land mass that is the dominant feedback?

Then you have a problem of definitions. Eccentricity is the deviation of the orbit from circularity. Obliquity is the inclination of the axis with respect to the orbital plane.

“You do realise how small insolation changes are relatively – that they balance out in an energy sense globally – and that it’s the ice and snow response on northern land mass that is the dominant feedback?”

Those are you particular assumptions. Why would anybody else realize them?

But it is not assumptions – there are warmer summers and cooler winters – the ITCZ shifts. A change in obliquity does not, by itself, alter the annual global mean insolation received by Earth.

Lower obliquity increases the insolation throughout the year close to the equator (from 10°S to 10°N), while higher latitudes experience a general increase in winter insolation and a decrease in summer insolation.

OK – small changes.

The principal cause of this global climatic shift was the redistribution of solar energy as the northern summer insolation decrease reached its maximum rate. This redistribution of solar energy, due to orbital forcing, produced a progressive southward shift of the Northern Hemisphere summer position of the Intertropical Convergence Zone (ITCZ).

The ITCZ shifts annually but as summers cool due to obliquity the shifts – both north and south – are less pronounced and lower latitudes warm.

This accompanied a pronounced weakening of summer monsoons in Africa and Asia and increased dryness and desertification at around 30°N latitude in South America, Africa and Asia.

There was a shift from dominant La Nina to dominant El Nino some 5000 years ago. Global hydrology shifted dramatically. South America – btw – misses the 30°N latitude and tends to more rainfall in El Nino.

The associated summertime cooling of the NH, combined with changing latitudinal temperature gradients in the world oceans, likely led to an increase in the amplitude of the El Niño Southern Oscillation (ENSO).

It is a big leap – without much in the way of justification. The shift to more intense and frequent El Nino – to be more precise than a change in ENSO amplitude – occurs at the same time as an increase in solar activity – and that mechanism seems more obvious as I described.

I referenced this earlier – it is a Law Dome ice core record. More salt is La Nina – and more rain in Australia, Indonesia, Africa and with influences on the Indian and Chinese monsoons.

The medieval and modern solar highs are ‘associated’ with enhanced El Nino frequency and intensity – and lower solar activity in the intervening centuries with La Nina. The mechanism involves UV/ozone chemistry and the modulation of northern and southern annular modes. lower activity pushes storms and wind fronts into lower latitudes and spin up oceanic gyres resulting in enhanced upwelling. Upwelling is the origin of ENSO and not insolation.

I find your fundamental premise unconvincing – as I have said. Your approach generally is too cavalier – with an overconfidence in the precision of paleodata, an undue confidence in your abductive inferences and little inclination to entertain alternatives.

“A change in obliquity does not, by itself, alter the annual global mean insolation received by Earth.”

Obliquity increases steal energy from the tropics all year round and put it in both poles concentrated in the summer season. And it happens year after year for many thousands of years and if you think that the accumulated effect is irrelevant then you don’t understand anything. The evidence shows clearly that earth temperatures respond primarily to that. Why do you think there are 41 kyr cycles in earth temperatures?

“with an overconfidence in the precision of paleodata, an undue confidence in your abductive inferences and little inclination to entertain alternatives.”

I follow the evidence wherever it takes. I do not try to tell nature how things should be. I would be happy to entertain alternatives if they were supported by the evidence.

Of course obliquity changes global net energy. This was demonstrated in Tzedakis et al., 2017 (link provided above). The most likely way this is accomplished is by altering the Meridional temperature gradient that regulates how much heat is driven to the poles and lost there by radiation. Raymo and Nisancioglu 2003 have a very interesting take on this. Although they only talk about the early Pleistocene there is no reason it doesn’t still apply.

At the weekend there was considerable publicity here in the UK regarding the apparent proof-long dismissed by academics- that a catastrophic impact by a comet 10500 years ago caused the abrupt climate change.

In the first instance there is no net change in global insolation. This is just a fact of celestial mechanics. Hand waving about secondary effects just misrepresents what I was saying.

Using your graph – which I will accept at face value as it looks about right.

The glacial effects are due to ice sheet feedbacks. – and the decline in temperature after the mid holocene may be due to ice and cloud feedbacks from a decline in summer insolation at high northern latitudes.

But there is something else driving ENSO variability over the Holocene.

Your ITCZ theory is nonsense – and the ocean thermistat theory of ENSO is very unlikely. We could discuss that – but you keep returning to misrepresentation and irrelevancies.

Oh – the variability of ENSO is dramatic at all scales – including a 20th century increase in EL Nino frequancy and intensity. The mid-holocene transition occurred at the same time as the solar transition to higher activity. There is both data and a mechanism that I have discussed in detail.

The original comet-impact Younger Dryas (YD) hypothesis is from 2006 and came as a way to explain the disappearance of the Clovis culture in North America together with the mammoths and other megafauna. The hypothesis defended the entire North American continent burned from comet airbursts or impacts. As stated it had failed to gain traction due to dating problems and lack of evidence.

However a platinum spike at the YD boundary in GISP2 supports that something happened. The spike is unusual as it is iridium poor and doesn’t match terrestrial sources, but does not fit either usual metal asteroid or comet compositions. The authors state that:“One of the plausible sources of the Pt spike is a metal impactor with an unusual composition derived from a highly fractionated portion of a proto-planetary core.”http://www.pnas.org/content/110/32/12917.long
A nice way of saying they have no clue.
However the Pt spike also disproves the catastrophic fires hypothesis as the source of ammonium is about 30-40 years later.

In my opinion a possible impact joins the list of probable causes of the YD:
– It more or less fits the Heinrich cycle and displays some of its signatures.
– It coincides with a low of the ~ 2400 year Bray solar cycle low.

It is possible that they all joined forces and contributed to the YD. A cosmic-astronomical-oceanic coincidence.

However it must be said that the YD has been overstated. It was very strong in the North Atlantic region, and apparent through tele-connections in Antarctica and other places (China), but clearly it did not affect sea levels that only display a small inflection point at the time. Marine records all over the world support that during the YD the deglaciation essentially continued albeit at a reduced pace. It is clearly not the return to full glacial conditions that Don Easterbrook claims. Just a global delay with a stronger regional impact in the North Atlantic. It did sabotage however a warmer Holocene Climatic Optimum peak like the one displayed by the early Eemian.

Now back to the University of Edinburgh claim. This is a bad case of social “sciences” invading the realm of real sciences with absurd claims. There are two fundamental problems. The first one is of dates, and the second one is of imaginative interpretation of an evidence that is simply not there.

The stone that is carved with animal figures is at best 11,500 years old, but it could be even 1500 years younger. The Pt spike is 12,900 years ago. In the best of cases if the impact took place they are separated by 2150 ± 750 years. As the Daily Mail puts it:“This means that when the Gobekli stones were made, around 9,000BC (that is, approximately 11,000 years ago), the sculptors had the astronomical know-how to backdate the constellations, shifting their pattern by a couple of millennia. And they were working with information that had been passed down over 2,000 years.”

Scientists have a duty to be skeptical, but journalists and their readers clearly not. 2000 years is an awful lot of time for people that lived shorter, harder lives and had no way other than unreliable oral tradition to transmit knowledge, usually related to the immediate survival.

So when is an animal only an animal and not a constellation? The original paper is available and in the appendix we can see how the animals are spread in the column without any particular disposition that we know, and we can see how the “researchers” have “matched” the animal images to groups of stars of their choice, connected by lines of their choice. Compared to that Schiaparelli’s Martian canals is hardcore science.

To me the article is solid evidence that anything can get published these days in a “scientific” journal, in this case the previously unheard of International Journal of Mediterranean Archaeology and Archaeometry, published by the unheard of University of the Aegean. I wouldn’t be pleased with the quality of my education if I was studying at the University of Edinburgh School of Engineering. It is also more indication that science dissemination should not be left in the hands of journalists without judgment.

Baseless assumption. You speak as if you know better than anybody else what happened and what was the cause. Not very scientific. Nobody denies that ice-albedo feedbacks were acting, but again ice is a consequence of cooling and winter precipitation, not a cause. Cause/effect confusions are very common in science.

“But there is something else driving ENSO variability over the Holocene.
Your ITCZ theory is nonsense – and the ocean thermistat theory of ENSO is very unlikely.”

Again and for the second time. You just don’t read what I write. ENSO variability could be driven by changes in the Equator-to-Pole temperature gradient (EPTG). Whether you think something is nonsense or unlikely is irrelevant. These things are determined by the work of experts that have made a profession out of studying it, not by aficionados like you and me.

Thanks for that. Having been brought up on Eric von daniken who was plausible until you looked behind the curtain, I had put this finding into much the same category.

Mind you, the stone column is inherently interesting and there are lots of anecdotal reports of some cataclysmic event. Whether any of them were real and whether the column will ever be properly interpreted is another matter.

As an aside some years ago I enjoyed the book by maxwell about the Chinese treasure ships sailing through the arctic. However it was thoroughly debunked and I joined in with this.

Having see the mountains of documents at the Scott polar institute in Cambridge and re read the book and checked some of the sources I would not now dismiss it all out of hand.

There are very many things we do not know about the last 10000 years of human history and the climate they lived under and many people are far too certain that they know more than they actually do.
Tonyb

“Baseless assumption. You speak as if you know better than anybody else what happened and what was the cause. Not very scientific. Nobody denies that ice-albedo feedbacks were acting, but again ice is a consequence of cooling and winter precipitation, not a cause. Cause/effect confusions are very common in science.”

Unbelievable. The ice sheet feedbacks were the major cause of cooling through changes in albedo.

‘Again and for the second time. You just don’t read what I write. ENSO variability could be driven by changes in the Equator-to-Pole temperature gradient…’

Again and for the umph time – I suggested that I preferred a different explanation and supplied both references and a mechanism. It explains both mid-Holocene change in ENSO and extreme variability over the Holocene – including the 20th century – in a way that sm,all and slow changes in insolation from orbital variations cannot despite the handwaving.

Some 5,000 years ago there was a change from dominant La Niña anomalies to dominant El Niño – that dried the Sahel. Just 3,500 years ago there were a long series of El Niño with red intensity greater than 200 and civilisations fell. For comparison – red intensity in the ‘monster’ 1997/1998 El Niño event was 99. There are quasi periodic 2000 years peaks in El Niño intensity. The 20th century saw a change to more frequent and intense El Niño as we a shift in the frequency of the oscillation.

Climate “Science” is a science. The very starting point should have been to demonstrate that the temperature variation over the past 150 and 50 years was statistically different from the previous 11,000 years. When you test the Hypothesis that Climate Change is of Natural Causes, it doesn’t get rejected. There is nothing statistically different about the past 150 and 50 years even if you use the “adjusted” NASA/NOAA/CRU data. They can’t even “adjust” the data enough to make their case. Combining the long term thermometer records like Central England, and the Satellite record, rejection isn’t even close. Using the proper unadjusted data sets, combining them with any ice data set you want, and you won’t reject the Null. Not even close. Also, all the Ice Core Records showed previous warming and highly variable temperatures, none of which were due to man.

Simply applying the scientific method to climate science destroys the AGW theory, even if you use the “adjusted” data.

Personally, I’m glad to see climate scientists actually using the scientific method. Had they done this back in 1990 we wouldn’t be in the mess we are in today.

Thank you for this interesting and informative post. The conclusion #1 says the climate has been cooling and drying for the past 6000 years. Scotese (2016) says the average temperature over the past 650 Ma was 7C warmer than present. The time duration of the Holocene is just 0.002% of the 650 Ma period Scotese refers to. Both these time periods (650 Ma and 11.5 ka), and your conclusions #1 to #3, seem to give a consistent message: Evidence is lacking to nonexistent to support the contention that human caused global warming, if it does occur, would be dangerous or catastrophic; in fact there seems a lack of evidence to support the contention that human-caused global warming could cause net negative impacts this century. That is, or GHG emissions may be a net positive for human wellbeing and the global economy through this century.

I find it disturbing/annoying the way the Marcot et al reconstruction understated the 8.2 k event illustrating the lack of sensitivity in their methods. BTW, the modern tail of the proxy record shown in the first illustration is the modern temperature record, not a reconstruction. This is very misleading.

Yes. It was done on purpose to eliminate from the data any trace of climate variability, leaving only modern climate change. It is an example of agenda-driven anti-science. But the modern tail was not the modern temperature record, it was statistic mistreatment of the reconstructed data.

Primary and secondary associated effects due to changes in solar activity are being overlooked. Very low solar conditions will promote a higher albedo thus lower temperatures due to an increase in global cloud coverage, snow coverage ,increase in volcanic activity , a more meridional atmospheric circulation while overall sea surface temperatures drop.

The geo magnetic field weakening compounds this.

Solar is going to be very weak going forward ,the orbital factors Javier mentions are on balance also favorable for cooling as obliquity is decreasing, precession( aphelion) still taking place during N.H. summer. In other words Milankovitch Cycles favor cooling going forward. This trend has been in pace since the end of the Holocene Optimum.

“The Mid-Holocene Transition, caused by orbital changes, brought a complete change in climatic mode, with a decrease in solar forcing and an increase in oceanic forcing….”

This is the clue as to the cause of the transition from MWP to LIA and LIA to Modern Warm Period. The LIA is classed as a North Atlantic Cold Event, when AMOC slowed, probably forced by declining solar variability, mediated via the transition to negative NAO, probably itself teleconnected to ENSO activity in the Pacific. It cannot be coincidental that research suggests El Ninos were far more frequent during the LIA than during the MWP.

There were nine confirmed cold events during the Holocene, occurring at 11.1 kyr, 10.3 kyr, 9.4 kyr, 8.1 kyr, 5.9 kyr, 4.2 kyr, 2.8 kyr, 1.4 kyr, and 0.4 kyr. The first four were probably driven by freshwater hosing dramatically slowing AMOC. The 5.9kyr event, corresponding to the end of the African Humid Period was the first cold event driven primarily by oceanic changes forced not by freshwater hosing but by declining solar activity. Thereafter, solar variability dominated North Atlantic Cold Events, the last of which was the LIA. So the MHT marked the transition from a very warm orbitally forced climate where polar ice melt drove dramatic slowdowns in AMOC to a cooler climate where solar variability/ENSO drives more moderate slowdowns in AMOC.

This is great stuff. Steve McIntyre has been saying for some time that good studies of the Holocene are needed to put the last few centuries into perspective. Mosher now seems to agree. Compare to: Prof Tom Anderson from the National Oceanography Centre, Southampton, who recently gave a public talk: (https://notalotofpeopleknowthat.wordpress.com/2017/05/01/prof-tom-anderson-shows-his-ignorance/)
Quoting:
He refused to look at data someone had brought showing the divergence of the models from observation.
He wouldn’t discuss the fact that similar temperature changes had occurred without CO2 (as he “wasn’t an expert in historical temperatures”)
He wouldn’t discuss the fact that Ice Ages had occurred without a CO2 signal (as he “wasn’t an expert”).
He wouldn’t accept the Medieval, Roman & Minoan Warm periods were hotter than present (as he “wasn’t an expert in historical temperatures”)

“Steve McIntyre has been saying for some time that good studies of the Holocene are needed to put the last few centuries into perspective.”

I made a comment at Steve’s blog Climate Audit that perhaps he should try to do a new reconstruction of Holocene temperatures given his expertise in proxies and his good understanding of statistics. Our knowledge has increased considerably in the last 10 years, and clearly Marcott et al., 2013 effort is unsatisfactory, due to his limited proxy choice, weird smoothing methods, redating of proxies, and faulty statistics.

Thanks Javier, interesting piece, I will have to re-read it again later.

I apologize if you already answered this, but can this model predict roughly how long we have until the next glaciation, and if so what does it predict? I’m not sure if the answer is robust enough to drive policy but it might serve for debate, and lately I’ve been worrying what might happen to humanity when the fossils and fissionables run out (perhaps sometime in the next few thousand years).

Is not really a model, but a review of the evidence. I looked into the issue of the present interglacial extension in the first part of the series. Since this interglacial is of standard astronomical characteristics, it should last about 2000 years more. You can read more about it here:https://judithcurry.com/2016/10/24/nature-unbound-i-the-glacial-cycle/

I am sure Peter Clark’s team (Marcott et al., 2013) was well aware that their reconstruction was at odds with the evidence and interpretation from many other groups. I guess they probably think that they are right and the others wrong. Over time more knowledge and evidence will accumulate and in my opinion it is likely that their view will not stand well the test of time.

Dynamically, both the PDO and NPGO are the oceanic expressions of atmospheric variability in the midlatitude Pacific [Chhak et al., 2009]. Specifically, the PDO is predominantly driven by variability in the Aleutian Low (AL) — the first mode of sea level pressure anomaly (SLPa) variability in the North Pacific [Trenberth and Hurrell, 1995], while the NPGO is dominantly forced by variability associated with the North Pacific Oscillation (NPO) — the second mode of North Pacific SLPa [Walker and Bliss, 1932; Rogers et al., 1981]. From an atmospheric perspective, both the AL and NPO have been linked to changes in weather patterns over North America, particularly changes in storm tracks, temperatures, and precipitation [Seager et al., 2005; Linkin and Nigam, 2008; and references therein]. ENSO and the North Pacific Gyre Oscillation: an integrated view of Pacific decadal dynamics,
Di Lorenzo1* E., N. Schneider2 and K. M. Cobb1, J. C. Furtado1 and M. A. Alexander3

There is an idea called the ocean thermostat hypothesis -in which heat input is the dominant determinant of ENSO dynamics. This is not likely. The modes of ENSO and the PDO – linked modes of climate variability – originate in upwelling in the eastern Pacific. The Pacific ocean gyres – both hemispheres – are spun up in negative phases of the polar annular modes – that are otherwise known as the AO and AAO.

Any reduction in global mean near-surface temperature due to a future decline in solar activity is likely to be a small fraction of projected anthropogenic warming. However, variability in ultraviolet solar irradiance is linked to modulation of the Arctic and North Atlantic Oscillations, suggesting the potential for larger regional surface climate effects. Here, we explore possible impacts through two experiments designed to bracket uncertainty in ultraviolet irradiance in a scenario in which future solar activity decreases to Maunder Minimum-like conditions by 2050. Both experiments show regional structure in the wintertime response, resembling the North Atlantic Oscillation, with enhanced relative cooling over northern Eurasia and the eastern United States. For a high-end decline in solar ultraviolet irradiance, the impact on winter northern European surface temperatures over the late twenty-first century could be a significant fraction of the difference in climate change between plausible AR5 scenarios of greenhouse gas concentrations. http://www.nature.com/articles/ncomms8535

While ENSO dynamics change between glacials and interglacials – it is first of all less relevant to centennial scale climate change – and secondly it seems quite difficult to come to a conclusion on whether it resembled an El Nina or La Nina state. It may be neither but – like today – characterised by an alternation of states. The isotope δ18O is enhanced by El Nino and depleted by La Nina – but it remains difficult to determine the dominant state. There is little enough agreement on this – and reliance on a single 2002 document is unwise.

That the dynamics change is reflected in δ18O variance.

With greater variance at the last glacial max, reduced in the early Holocene, less at the mid-Holocene and more since. Interesting and worth puzzling over.

You may note the increase in El Nino intensity following the increase in insolation at the equator – but it also follows an abrupt shift to higher solar intensity. Finer scale analysis suggests a solar origin to much of the extreme ENSO variability. Something that can’t be explained by a slow change in equatorial insolation.

Javier,
There are many interacting variables in your classical essay. Has any author considered a format that allows a different grasp of data, such as an input/output style? I have in mind a 2D square set of boxes, in which the interaction of items on the Y axis is described for each of the X axis items in turn.
You describe 2 versions of temperature change in the Holocene, say Marcott’s and yours for brevity. In a two way table, one can compare those items that influence temperature and so, quickly find likely points of divergence for more detailed study.
In the ideal world, such an approach might help work out if glaciers advance or retreat with decreasing temperature, linking to snowfall rates and to any other relevant variable with both qualitative and quantitative links.
Such an approach might lead to plausible constraints on a number of the variables.
Geoff

You are right, but isn’t that the basis for climate models? They link every part of the climate through physical equations and parameters that are obtained from past climate change observations. As long as they are understood as projections of our imperfect knowledge, they are useful tools for precisely the types of things you are saying.

Javier,
You are right also, but I was asking about a more open, visible layout where each box could be inspected to refine its various dependencies. Maybe I chase too grand an objective. Yours was a lovely essay, thank you. Geoff.

However, as is very common, you minimise the contribution of eccentricity changes to climate forcing, which is very weird! While precession and obliquity have no impact on the global total solar insolation, eccentricity does, driving total annual insolation as 1/√(1-e²). Total annual solar insolation has fallen steadily throughout the Holocene (at constant candle).

“you minimise the contribution of eccentricity changes to climate forcing, which is very weird!”

Well, the reason for that is that the experts consider that the contribution to climate change directly from eccentricity is very small. One usually doesn’t see the forcing from eccentricity plotted at the same scale as from precession and obliquity. However an illustration was used in my first article on the glacial cycle:

Thus most researchers consider that the main role of eccentricity on climate change is not direct, but through modifying the values of precession and obliquity according to ~ 100 kyr and ~ 400 kyr cycles.

There is a ‘big spanner’ loose in the above works, the existence of which is little perceived. Allow me, please, to point to its possible hideout.

To start; in fig 37 curve ‘c’ is scaled to mimic curve ‘b’. Two points to note here. The scale is deceptive because from 9k to 2k the change is only 0.4deg. Secondly, pre 10k the mimicking ends abruptly. Shows that something is wrong.

Refer now to fig38, and 42. Curves from these – as well as others- have been used to construct a series of proxies intended to correlate ‘hiccups’ to abrupt changes noted in archaeological structures that also show evidence of abrupt changes in their design evolution. These may be seen at the link below:https://melitamegalithic.wordpress.com/2017/02/24/blog-post-title-2/

The contention here is that obliquity changes do not follow the historically assumed character and are ‘abrupt’ and greater than thought. Those changes occurred between 6200 and 2000bce and were abrupt and with cataclysmic consequences, and the values have been recorded in the dimensions of ancient structures. Note for example that an obliquity change effects polar ice temps in opposite manner than to equatorial ice temps, and that case is evident in the GISP2+Vostok compared to Kilimanjaro.

Javier, thank you for all the great articles. Clearly, the “Holocene Conundrum” is the most interesting puzzle piece as it directly relates to CO2 sensitivity and is at odds with our modeled understanding of Holocene forcings, as you point out. Question: do the climate models factor in the increased albedo from NH glacial advance due to the waning NH insolation due to precession?

Also, since the consensus assumption is that Holocene pre-industrial increase in CO2 was lag of ocean solubility catching up to the new temperature (GMST) shifted equilibrium, I am wondering if there are other lags leading to “conundrums” seen in past interglacials. And, can Milankovitch forcing (NH glacial extents) vs. CO2 vs. global temp be modeled in past interglacials now, or if better ice core resolution is achieved?

Javier – thanks for the response. I just followed my link and it worked, I’m afraid my it skills are exhausted. If you could have another go, maybe it would work. Look at the second chart. Admitting the brains ability to see patterns where none exist, it seems very hard to argue no significant role for eccentricity.

The link worked this time (perhaps a server problem the first time). Your temperature fit to orbital parameters highlights the problems we are discussing. The eccentricity introduces a strong deviation and the fit would be much better without eccentricity, only with obliquity and precession.

But I find it satisfying that you find the same lag between obliquity and temperatures as I do (~ 6000 years).

Well, this took too long: my ISP had withdrawn support for my webspace, and it’s taken me a while to find the obvious alternative. Here are some links, which I hope illustrate the point. Although the total eccentricity forcing at any latitude is small compared to that from precession and obliquity, that is a bit like saying that the seasons are not important, the key to insolation is whether it is day or night – true, but missing something! Look at this picture, and tell me that eccentricity forcing is not a key driver of (de-)glaciation:

As I posted yesterday at WUWT: there are 79 ten-thousand year intervals in the ice core record I’ve used. In 49 of them, the direction of change of temperature matches the direction of change of the eccentricity forcing. In 30, the direction differs. The chance of 30 or fewer heads in 79 tosses of a fair coin is around 2%. Without replying on visual impressions, that I think is concrete statistical evidence of a strong link between the two.

As we’ve noted before, lags in the system probably mean that one could find an even better relationship if one sifted through various lags.

Holocene climatic changes for the big picture are due to land/ocean arrangements /Milankovitch Cycles but in the smaller more abrupt Holocene climatic changes one needs to superimposed solar activity and geo magnetic field strength along with volcanic activity /ENSO.

The following extract from the link below is an eye-opener, and should perhaps encourage to ‘think outside the box’
“What should be clear from this small foray into the subject is that there is no “Milankovitch theory”.

There are many theories with a common premise – solar insolation changes via orbital changes “explain” the start and end of ice ages – but then each with a contradictory theory of how this change is effected.

Therefore, a maximum of one of these theories is correct.

And my current perspective – and an obvious one from reading over 50 papers on the causes of the ice ages – is the number of confusingly-named “Milankovitch theories” that are correct is zero.”

There have been significant advances in the understanding of how interglacials are produced by a combination of orbital changes and climatic factors, since that blog entry was published almost 4 years ago.

I am not trying to diminish Milankovitch’s contribution. Simply, his theory that the glacial cycle is due to changes in summer insolation at northern high latitudes is not supported by the data. This happens all the time. The huge majority of hypotheses are wrong and that does not detract from the scientists that propose them.”””

What I point to are evidence of step changes in obliquity – evident between ~5400bce to 2000bce – which current theory on obliquity (ever since Stockwell/Newcomb) excludes and does not even consider. From paper by D’Andrea et al “Glacier response to North Atlantic climate variability during the Holocene” late last December I have been able to date the changes, as these appear also in several other proxies. In the link in earlier post you may note dates that show up across various research (Notable one by P DeMenocal re Sahara abrupt change circa 5500 BP, ~3500bce). In what I studied -ancient calendars- these also show as major cataclysmic events.

I find your conjecture that there have been abrupt changes in the obliquity of the earth’s axis totally unconvincing.

The archeological and climatic evidence that you use is subject to interpretation, and the proposed abrupt changes in obliquity do not fit into our astronomical knowledge. Changes in obliquity have been reconstructed with great precision based on the known movements of the planets and they fit very well climatic records for millions of years. There is no room for the drastic changes you propose.

Your conjecture is not supported by any serious scientific peer-reviewed article in a journal, or scientific book. Therefore it does not exist for the world of science. You should consider the very likely possibility that you are wrong. If it is any consolation, most hypothesis, even serious ones based on solid science, are wrong. This is because there are unlimited explanations to any phenomenon, but only one is correct.

Yes, thank you, a nice article by a lot of well known climate scientists. It underscores once more that Greenland Holocene climate is different from global Holocene climate or even Northern European Holocene climate. A lot of people extrapolate Holocene Greenland ice cores to global climate, which is a mistake. For example it is well known that Greenland climate shows an inverse response to solar forcing, and warms during periods of low solar activity, as the article says. I am not convinced, thought that volcanic forcing can act on centennial to millennial time-scales. It is based on modeling, and other proxies disagree.

Javier is under estimating this prolonged solar minimum we are in, he does not accept the major volcanic /solar connection ,gives to much credence to co2 (which has zero impact on the climate) and can not address abrupt climatic changes in an adequate way in my opinion.

Javier
Thanks! – once again an excellent review of a critically important issue in the climate debate. Just what is the scale and significance of climate change in the last couple of centuries in the context of the Holocene? Should it be considered unusual for climate to change? Does the term “climate change” even have any meaning or is it a vacuous tautology?

One issue regarding proxies is that the isotope based proxies, both of ice cores and also marine / lake sediments, seem at odds with the biological proxies of pollen, midges as well as the anomalous alkenone proxy favoured by Marcott. Generally the isotope proxies show a picture of higher amplitude temperature swings during the Holocene while the biological proxies show a smoother lower amplitude trace. Indeed some biological proxies included in Marcott’s stir-fry scarcely even resolve the Holocene itself from the LGM (last glacial maximum).

On this basis I would like to see a case argued for focusing on the isotope proxies only, and for closer examination of what the biological proxies are actually proxies of. They are so divergent that they cant all be right and it makes little sense just stirring them all together in the same saucepan.

what is the scale and significance of climate change in the last couple of centuries in the context of the Holocene?

This is really a tough question, and it cannot be demonstrated whether the changes are unusual or not. I can only give you my honest, unbiased opinion.

The concept of global average temperature does not exist outside the algorithms of modern computers. Some proxies are more sensitive to summer temperature changes, others to winter changes, and some respond to both but perhaps being most sensitive to one. While nearly all proxies show an important warming in the 20th century, even the question if we are now warmer than the peak of medieval warm period cannot be given a definite answer. My opinion is that we are probably warmer than the MWP but not as warm as the Roman warm period.

In the context of Holocene temperature evolution this is a clear departure from Neoglacial trends. This by itself should not lead us to jump to conclusions. While for the last six millennia, every millennium has been colder than the previous, the data for the present millennium only has 17 years. Plenty of time to get the average below the last millennium. As we will see in the next part of this chapter, increased amplitude in climate change oscillations is the trademark of a cooling world, and that means also increased warming when it is time for warming.

I would be more concerned if this was a time when the world should be cooling, but it is not. Whether we had increased GHGs in the atmosphere or not, this (until ~ 2100 AD) was a time for warming. It is very likely that GHGs have increased the warming the world has experienced in the last 40 years, but it is also very likely that the natural contribution is a lot more important than models and IPCC are accounting for.

Generally the isotope proxies show a picture of higher amplitude temperature swings during the Holocene while the biological proxies show a smoother lower amplitude trace.

I think this is partially due to a higher sensitivity and a more local nature of isotopic changes. Kobashi et al., 2013, has an average of six Greenland ice cores (red curve below) where the variability is a lot smaller than from just one.

Besides, most biological proxies respond almost exclusively to summer temperatures, that might show less variability than winter temperatures. And on top of that biological changes are slower and tend to integrate decadal changes rather than annual changes. I think they both provide important information and we should try to extract a more general picture from both.

Thanks for this very informative reply. About the bio proxies,“I think they both provide important information
yes indeed, but about what? You nicely point out the reasons why they indicate several things but not necessarily “global temperature” – nebulous though this concept is. The bio proxies are utterly divergent while the ice core and sediment isotope records at least have recognisably similar shape giving them much more authority.

Would not averaging several ice cores run the risk of a spurious smoothing due solely to the time stamping uncertainty of all of them relative to eachother? Unless one can be 100.00% sure that time stamping of different proxies is identical and accurate, then I would avoid smoothing them together at all.

By analogy, a dozen timing devices record a person’s heart beat. All the timing devices have small time error, plus or minus a fraction of a second, and a speed error also. However the individual errors do not prevent any individual recording by any of the devices from giving a reasonably accurate record of the person’s heartbeat. But what happens if you average them all together? The person is pronounced dead – the heartbeat is smoothed to a flatline.

About the bio proxies,
“I think they both provide important information
yes indeed, but about what?

Bio-proxies are very useful. Macro plants only grow within a range of conditions that are species-specific. Pollen frequencies give information about the ecosystem as they inform of plant genre abundance. Together they allowed the first paleothermometry, and the Holocene division in pollen zones that allowed a quite accurate reconstruction of past climates 100 years ago. They are still very much in use.

coccoliths allow the reconstruction of ocean temperatures at different depths, together with salinity changes and ocean stratigraphy. Alkenones also allow the reconstruction of sea surface temperatures. Today scientists set catchment traps at the bottom of the oceans to measure the rates of coccoliths sedimentation to control for conditions for interpreting the cores. We know of the likely cause for D-O events from changes in coccoliths living at the interface with the halocline in the Norwegian sea. The relative levels between coccolithophores, diatoms and dinoflagellates also allow temperature reconstructions.

IP25 (Ice Proxy with 25 carbon atoms), is a proxy for sea ice in the Arctic. It is the main (almost only) source of information on past sea ice levels in the Arctic.

This is only a very limited list, and new biological proxies are being added all the time.

Of course every proxy has its problems and limitations, and none is free of contaminating conditions like sedimentation rate, depending on more than one climatic factor (insolation, temperature, precipitation), so they are all subject to interpretation. But this problem is not exclusive of biological proxies. For example, isotopic determination in speleothems from cave stalagmites also shows problems and limitations. Two spelothems from the same cave and different stalagmites can give quite different isotopic profile. They are also subject to interpretation.

Would not averaging several ice cores run the risk of a spurious smoothing due solely to the time stamping uncertainty of all of them relative to each other?

Every proxy has noise over which the signal has to be revealed. Although averaging might affect annual signal due to age uncertainty, it is likely to improve decadal signal by reducing annual noise. Ice cores can be dated quite precisely one to each other thanks to eruption signals and other chemical peaks. The time uncertainty between those markers is of only a few years for the Holocene. And after all climate is usually defined in a multi-decadal level with annual variability being considered noise.

Javier, Thanks for your wonderful article (and Andy May as well. It certainly has me thinking. You point out that there is problems with the hundred year cycle and point to obiquity as being the deciding factor. I am a layman but would like to take exception with that assessment anyway. First of all I would like to point out my previous assumptions. With regards to length of cycles. Excentricity between the end of eemian and the start of Holocene is seen as taking between 128 years and 106 years. The bell like curve of apsidal precession conforms with both eemian and Holocene lasting 23 to 26 thousand years. According to Duncan Steel this coorelation shows the peak on December 21st and we are on the downward slope somewhere around January 8th. It taking 68 years for each day. It appears to me that excentricity and the apisidal math the glacial cycles better than obiquity. That has been my understanding. Now you point out that obiquity is the strongest cycle of the three and cite Wikipedia and others. I have no problem with that. My point here is that the apisidal and excentricity cycles better match the glacial cycles.

You pointed out on a post that if Mercury had an elliptical orbit with enough length it would be frozen too. Now the difference between the near round orbit of Earth and full excentricity is said to be 5 kilometers or 3.1 miles. Supposedly it is still a weak forcing. It should be noted that the weak forcing of a quiet sun was enough to cause the last little ice age. A solar scientist of some renown (her name escapes me) pointed out we are somewhat uncertain at this point and know very little about things like UV radiation.

Milankovich never studied orbital inclination. So there are 4 factors that determine glaciation. Three of them have to do with forcing. Both apisidal and orbital plane inclination take the Earth to a different part of solar forcing that is different from straight facing the solar equator. My point here is that we have four factors influencing glacial events. Why would one place most of the effect coming from just one factor especially when it’s cycles don’t really coorespond with glacial events.

My views received a very important support when Paul Tzedakis and Michel Crucifix, two leading experts in past interglacials, and Eric Wolff, a leading expert in ice cores, published recently an article defending every point I had made in my article, even with similar figures.

They stopped short of saying that the 100 kyr cycle is an artifact, as I do, but they say:“As a result, interglacials of the past 800 kyr do not occur every 100 kyr and are not always preceded by one of the traditionally numbered glacial terminations defined over this interval.”

Current scientific understanding is moving from a 100 kyr cycle that nobody can explain satisfactorily, and that creates numerous problems, towards a 41 kyr cycle modified by precession and feedbacks, that explains the entire Pleistocene and solves those problems. My proposal is in no way outlandish.

Javier, Thanks for the reply. I did read your first article and that is what I was responding to. I haven’t been able to read or respond on here for awhile but normally I’m a regular. I responded here since it is most recent so you might see my comment. No, I don’t think your take is outlandish and you reason well and presented it well and I want to thank you for increasing my understanding. I simply wanted to express my view that I believe it is the combination of all four cycles that bring about glaciation. Again thanks for this information; I will continue to think about it reread your work and contemplate it further. Muchos Gracias Senior. ☺

I simply wanted to express my view that I believe it is the combination of all four cycles that bring about glaciation.

And formally you are absolutely correct, as the climate of the earth integrates every forcing, and together with intrinsic chaotic behavior and internal variability produces an output.

What we are trying to determine is how much of the output is due to each factor, and distinguish between cause and effect, forcing and feedback, first order and second order factor. In truth almost all scientists agree on the factors that influence the climate. The main disagreement is how important they are for the final response.

Once said that. In the glacial cycle the main question is how an interglacial is determined. The problem is why some deglaciations go all the way to an interglacial, while others are aborted. What causes glaciations is much easier. The fall in obliquity ALWAYS produces a glacial period, several thousand years later (see figure. No exceptions). Now some people (and scientists) believe this time will be different. In some thousand years somebody will find out if they are correct in claiming exceptionalism for the Holocene.

I continue to believe in a role of ecentricity despite the smallness of the forcing, since if (as I believe) the system is quasi-chaotic then small forcings can rule the day.

It is very clear from Javier’s first figure 35 that a clear and consistent correlation exists of glacial cycling with obliquity. However two other things are clear. One is that something modulates the system’s response to obliquity. Sometimes a big interglacial spike closely accompanies an obliquity peak – e.g. the Eemian and the Holocene. However at other times an identical obliquity peak elicits onl a pitiful stub of a response, hardly reaching significance, e.g. 470,000 and 670,000 ears ago. Something is modulating the glacial-interglacial system’s response to obliquity. This could very well be eccentricity.

Interestingly when an eccentricity peak coincides with an obliquity one then you get a regular interglacial, but when the eccentricity peak comes halfway between obliquity peaks then you get “double-header” interglacials, such as about 220,000 and 600,000 years ago. These also coincide with the largest amplitude eccentricity oscillations. Conversely the eccentricity peaks at lowest amplitude give the most cleanly defined interglacials. This is the opposite of what you would expect if eccentricity was forcing (even jointly with other cycles) the glacial cycle. This just deepens the mystery.

Chaos has to be brought into this. The paper below is about the chaotic dynamics that can occur when an oscillatory system – a tidal inlet – is forced by multiple tidal wave forcings. A quick look through the paper of a few seconds only will show you that the oscillatory response in the tidal inlet linked to the sea by a narrow neck, quickly become very complex and chaotic and that attractors emerge. WHy s no-one applying this kind of analysis to the glacial-interglacial cycle, also under influence of several weak and variously inter-related Milankovich forcings?

I continue to believe in a role of ecentricity despite the smallness of the forcing.

Well, everybody believes eccentricity has a role, including me. But eccentricity main role is not directly but through its modulation of precession and obliquity. Precession only changes seasonal insolation because the orbit is eccentric. If the orbit was circular there wouldn’t be any orbital precession, and axial precession would be irrelevant in insolation terms, as the wobbling of the axis would not alter the part of the earth facing the sun at apogee or perigee as there wouldn’t be any apogee or perigee in a circular orbit. It would only affect the position of the stars in the sky. Eccentricity also affects obliquity insolation, as for the same inclination insolation changes if the pole is facing the sun at perigee or apogee. With a circular orbit obliquity insolation would not be modulated by eccentricity and would depend only on the inclination of the axis. So, what are the changes due to eccentricity?

when the eccentricity peak comes halfway between obliquity peaks then you get “double-header” interglacials, such as about 220,000 and 600,000 years ago. These also coincide with the largest amplitude eccentricity oscillations.

Exactly. When eccentricity is very high its modulation produces very strong northern summer insolation peaks every 23 kyr (precession peaks). This is very helpful for obliquity and so at every obliquity peak, with the help of increased northern insolation, an interglacial is produced. If eccentricity was high all the time, the earth would get interglacials every 41 kyr, as was the case during the early Pleistocene, when the earth was not as cold as is now.

Conversely the eccentricity peaks at lowest amplitude give the most cleanly defined interglacials. This is the opposite of what you would expect if eccentricity was forcing (even jointly with other cycles) the glacial cycle. This just deepens the mystery.

Not really. When eccentricity is low, precession is low, and northern summer insolation is low. Then it is difficult for obliquity alone with little help to start an interglacial. Another factor is required. This factor is defined as “time-dependent ice sheet instability” by Tzedakis et al., 2017, and it is a summation of all the negative feedbacks that accumulate as the ice sheets grow and that are ready to push the world towards an interglacial given the right conditions. Between others they are an ice border that has pushed so far south that will retreat very fast when conditions change. An ice sheet that extends so low below current sea levels on continental platforms that as soon as the melting starts is going to be quickly melted by rising sea levels. A high dust production due to harsh glacial maximum conditions. All these will cause a very strong ice-albedo decrease feedback. That’s how the world gets out of glacial conditions when eccentricity is low. That’s why we get aborted interglacials when the melting doesn’t go fast enough and the obliquity peak is reached without an interglacial being produced. Feedbacks act as a strong spring that takes tens of thousands of years to stretch, and when released allow a faster melting of the ice sheets in the short span when obliquity is rising. When eccentricity is high enough they can be dispensed, as insolation is high enough to melt the ice by itself.

Javier
Thanks for this very nice explanation. It makes me wonder why this is not settled theory, why Milankovich forcing is still apparently questioned.

I have seen recent studies confirming that as ice sheets get bigger they get leas stable, both generating deeper cold but also requiring deeper cold to sustain them. This tension imparts nonlinear instability. Such a system is more susceptible, not less, to periodic forcing. Therefore the correlation with obliquity in your fig 35 is still too good to accept that for some cycles its periodic forcing ceases and something else takes over. The whole system looks like a nonlinear oscillator under multiple weak forcing (obliquity being the strongest).

“…Our simulations suggest that a substantial fraction (60% to 80%) of the ice sheet was frozen to the bed for the first 75 kyr of the glacial cycle, thus strongly limiting basal flow. Subsequent doubling of the area of warm-based ice in response to ice sheet thickening and expansion and to the reduction in downward advection of cold ice may have enabled broad increases in geologically- and hydrologically-mediated fast ice flow during the last deglaciation.”

– Marshall and Clark

The Ice sheets grow higher while the sea level drops. Water is raised up in elevation and stuck in place. Water is transported from the equatorial regions and stacked closer to the poles as ice. It is suggested that this is unstable past a point.

When moving in the direction of an interglacial, new cooler water is easier to warm. It is easier in equatorial region to warm cooler water. It doesn’t emit as much to the atmosphere. It is more efficient at warming the oceans.

It might be interesting to consider ocean salinity changes related to the sea level fall.

As with solar forcing there are immediate and long-term impacts for CO2. For solar forcing the 11-year cycle is immediately seen in the temperature record. For CO2 long-term impacts affect continental glaciers and ocean circulations. Also Hansen recognizes that greening is a positive albedo feedback that enhances CO2 sensitivity over longer terms.

Hansen had in mind the expansion of the forests into what is now Arctic tundra as happens in the iceless hothouse paleoclimatic states, which has a much larger effect on albedo, but the greening we have does darken the surface too.

In terms of forcing, AGW has already reversed the joint trend of obliquity and precession that was increasing Arctic ice and that had persisted since the Holocene Optimum, so it is much larger and faster. The trend now is twenty times faster and in the opposite direction from the Milankovitch trend. This is an important perspective to keep.

In terms of forcing, AGW has already reversed the joint trend of obliquity and precession that was increasing Arctic ice and that had persisted since the Holocene Optimum, so it is much larger and faster. The trend now is twenty times faster and in the opposite direction from the Milankovitch trend. This is an important perspective to keep.

You don’t know that. You are inventing and assuming. We only have 37 years of Arctic sea ice satellite pictures and you are already drawing unwarranted assumptions. Trends opposing Milankovitch forcing are very common and they often last several centuries. Arctic sea ice has a periodicity related to AMO. That’s why in the last 10 years Arctic sea ice has gone nowhere despite CO2 going from 380 to 410.

If it is clear that we don’t know the effect of CO2 on climate, how could you possibly know that it is several times larger than Milankovitch?

The CO2 effect on climate is what we are seeing. So far 1 C warming for half a doubling is right in the middle of where it is expected to be. No one is surprised. Also no surprise that Arctic sea ice is disappearing and Greenland is melting as a result of a century of such warming.

Such a vague statement does not belong to the science realm. After 38 years climate sensibility is still between 1.5-4.5 °K per doubling at 90% confidence. This means nobody knows. It even means there is a very small chance that climate sensitivity could be negative, so it cannot be ruled out completely.

No one is surprised.

Everybody is surprised. Nobody had a clue in 2001 that warming was going to be so small for the next 13 years. Nobody had a clue in 2007 that Arctic sea ice by 2017 was going to have the same extent. Nobody has a clue what the climate is going to do for the next 15 years. Whoever says otherwise is lying.

Also no surprise that Arctic sea ice is disappearing and Greenland is melting as a result of a century of such warming.

I guess you have no clue about the world you live in. Greenland is almost completely covered in ice all the time. There are several millions of sq km of ice in the Arctic any time of the year. Antarctica is buried in kilometers of ice. This defines that we are right now in ice house conditions. The coldest 10% or less in the history of the planet. Right now. To say that the world is warm is to lack perspective. We have not underwent a century of warming, we have underwent over three centuries of warming since the depths of the LIA. And all that has not made a dent in Antarctic ice. Greenland is losing a ridiculous amount of ice every year. It will get it back in the next cooling, no doubt. This is not a very warm interglacial, and is ending. Arctic sea ice has been retreating, but before the warming it was advancing and had reached to Scotland, isolating Greenland and Iceland during the winter, so I would say the retreat is a plus, not a minus. Frankly I do not know what you would be planning to do with all that sea ice if by any chance it comes back during our lifetime.

According to Milankovitch cycles we should now be at about the coldest in the last few millennia, but instead we are the warmest and getting warmer. GHG forcing exceeds 2 W/m2 and is rising steadily at over 0.3 W/m2 per decade. The most expected value of warming for that is 1 C. This is why I say no one is surprised at the last century of warming. You talk about 15-year spells like they are climate. Fifteen years is one and a half solar cycles which is a particularly bad interval to use because you alias in the 11-year cycle which is not negligible, being 0.1-0.2 C in amplitude. So if you look at 15-year trends over the century they are all over the place. The 15-year trend peaked just prior to 2000 at 0.3 C per decade. Meanwhile 30-year trends have been steady at just under 0.2 C per decade for several decades since the 1980’s. The people who defined climate as a minimum of 30 years knew what they were talking about. Paleoclimate data show us that by 500 ppm Greenland cannot keep its ice, and by the time you reach 700 ppm, neither can Antarctica. If you don’t consider CO2 you miss the big picture of what has happened in the last hundred million years.

According to Milankovitch cycles we should now be at about the coldest in the last few millennia

NO, that is an incorrect interpretation of both the effect of orbital changes and of paleoclimatic evidence from past interglacials. Due to their long period and slow changing nature orbital changes causes every millennium to be colder than the previous since 7000 years ago. Last time I checked, the second millennium AD was the coldest. After a low in the Bray cycle the planet always gets warming. This millennium only has 17 years (67 if we count BP). Plenty of time to get colder than previous.

GHG forcing exceeds 2 W/m2 and is rising steadily at over 0.3 W/m2 per decade. The most expected value of warming for that is 1 C.

The most expected has no meaning in science and the forcing of GHGs is a calculation based on assumptions. If nobody knows the climatic effect of increasing CO2, then it is obvious that nobody knows the value of the forcing. Assumptions are often wrong.

The people who defined climate as a minimum of 30 years knew what they were talking about.

There is no such definition. For example:“Climate: 1. the composite or generally prevailing weather conditions of a region, as temperature, air pressure, humidity, precipitation, sunshine, cloudiness, and winds, throughout the year, averaged over a series of years.”
There is no magic number of years that makes climate. As long as the period is of several years and stated, then we are talking climate. Periods of 15 years have a higher variability than periods of 50, and periods of a century have a higher variability than periods of a millennium. I can use your arguments against claiming exceptionality for the past century.

Paleoclimate data show us that by 500 ppm Greenland cannot keep its ice, and by the time you reach 700 ppm, neither can Antarctica.

This is simply not true. Paleoclimate data doesn’t show such thing. For a start we do not know what has caused Greenland and Antarctica to have ice. Then you cannot assign cause or effect status without proof. The correlation of temperature, ice, and CO2 during the Pleistocene does not allow to distinguish what is cause and what effect. What we know is that CO2 alone was not responsible for the temperature changes because it didn’t change enough. That alone suggest CO2 is unlikely to be the cause. 75 ppm between Last Glacial Maximum and Holocene start is puny. We also know that CO2 has been very limited during the Pleistocene. That also makes it unlikely to be the cause. And last the increase in CO2 from 270 to 410 ppm has not warmed Antarctica the least. Why should a further increase to 700 ppm melt it? You live in a state of fantasy with little connection to reality. You think that if you belief in something that makes it real. In the world of science you have to demonstrate things. It is a lot harder than believing in them.

Several points.
It looks like you agreed that the Milankovitch trend should still be downwards, which is what I said.
You don’t accept that we know anything about sensitivity and therefore want to disregard any value, even a central estimate. I can’t help you with that, but the one degree C warming we have had in the last century or so matches the expected amount from the forcing change. No one is surprised, except you.
Thirty years is the WMO definition. It is widely used.http://journals.ametsoc.org/doi/pdf/10.1175/2010BAMS2955.1
Fifteen-year trends are all over the place. Wait a decade and it can change 100% making it a useless measure of anything long-term. In contrast, 30-year trends have only change within about 10% since 1980.
Regarding paleoclimate. Prior to the Ice Ages, CO2 levels were higher and the earth was warmer. Arctic sea-ice was mostly absent. Prior to that it was warmer still and Greenland had no ice. Prior to that it was even warmer 35 million years ago and Antarctica had no ice. Sea levels were much higher. CO2 levels increase as you go further back too, and not by coincidence. Geological processes have been removing CO2 since about 50 million years ago in the Eocene when both CO2 and temperatures were at their last peak. This is common knowledge in paleoclimate and it is all understood in terms of GHG levels and forcing. I am not saying anything new here. Check out Richard Alley’s excellent 2009 AGU on the CO2 understanding in paleoclimate.

It looks like you agreed that the Milankovitch trend should still be downwards

Both Obliquity and precessional northern summer insolation will reduce for the next 1000 years, then precessional northern summer insolation will start to increase, but it can be demonstrated (Figure 14, Nature Unbound I) that the continuing decrease in obliquity will be the dominant factor for another 10,000 years.

You don’t accept that we know anything about sensitivity and therefore want to disregard any value, even a central estimate.

Well, it is a fact. We don’t know if the climatic effect of the added CO2 is going to be catastrophic (ECS ≥ 4.5), or harmless (ECS ≤ 1.5). A central estimate has no meaning under those conditions. Specially since paleoclimatology does not assign any special role to CO2 in controlling earth’s temperatures.

but the one degree C warming we have had in the last century or so matches the expected amount from the forcing change. No one is surprised, except you.

Don’t make me laugh. Nobody predicted that degree of warming a century ago based on science. After the fact we just think we can explain it and “No one is surprised” that we can explain it. Duh, we can explain anything afterwards. Even what the stock market has done. That has no value.

Thirty years is the WMO definition. It is widely used.

You prefer 30 years, fine with me. The problem is that if there is any change of conditions you are going to be 30 years late to understand and study it. That is why there are 400+ scientific articles on the hiatus or pause in global warming, because scientists don’t follow your advice.

Prior to the Ice Ages, CO2 levels were higher and the earth was warmer.

And CO2 levels were higher and the earth was colder. In the past 600 million years the earth has seen colder and warmer with more CO2. For all we know CO2 levels have always been higher than in the late Pleistocene, while temperatures have been lower than currently multiple times. Paleoclimatology does not support that CO2 is a first order factor in the determination of earth’s temperature.

Arrhenius a century ago had the idea, but not the most accurate data to be able to make that prediction of where we would be with 400 ppm. The science has been known for a century in an essentially unmodified form. He used a simpler form of water vapor feedback, but the idea was there that water vapor amplifies the CO2 effect.
The idea behind 30 years is don’t be fooled by pauses and jumps that cancel each other out on shorter terms. The past 30 years is a good example of this.
On CO2 levels in the last 100 million years, they have explained the global temperatures. The sun has also been getting stronger at 1% per hundred million years, equivalent to a CO2 doubling per 1%. As you go further back it would take a lot more CO2 to make it as warm as today. The Permian had lots of ice and lots of CO2, but the sun was 2-3% weaker too, and the earth had a different continental configuration too. This all matters. It is not one-dimensional.

The science has been known for a century in an essentially unmodified form.

A nice way of saying that nobody has been able to prove the hypothesis in a century, or we would not be discussing it.

The idea behind 30 years is don’t be fooled by pauses and jumps that cancel each other out on shorter terms.

Every change of trend, the start of the descent into the LIA, the end of the LIA and beginning of current global warming, started at certain point when temperatures stopped going in the previous direction. You might demand 30 years, but nature doesn’t.

On CO2 levels in the last 100 million years, they have explained the global temperatures.

Which means nothing in science, as most explanations are incorrect. In this case the explanation doesn’t even hold water. The earth has been both warmer and cooler with more CO2.

The sun has also been getting stronger at 1% per hundred million years, equivalent to a CO2 doubling per 1%. As you go further back it would take a lot more CO2 to make it as warm as today.

Another hypothesis that is based on assumptions, suppositions, and involves circular reasoning. The most likely factor compensating solar changing output is water homeostasis.

You speak of things that we don’t know, and hypotheses, as if they were facts. You don’t understand science, because you treat it as a religion. All these people are doing is proposing hypotheses that stay there who knows for how long, because we might never know. And our job is not to believe them, but to be skeptical of them, attack them, and demand more evidence, because the great majority of hypotheses are incorrect in all or part. Believing hypotheses that are supported by insufficient evidence is a fools way. You are asking to be wrong more often than not.

Proof is for mathematics. Science explains what we see in terms of basic building blocks. In this case it is the earth’s energy budget and the physics of greenhouse gases which explain why the earth has its current temperature and how the changing balance changes it.
You need to start with AR5 WG1 and say what you disagree with there. Or maybe it is Arrhenius or Tyndall where you diverge. You seem to believe Milankovitch that subtle energy balance changes have large effects, but I am not sure you see the effect of increasing CO2 in that light even though doubling it is like increasing the solar strength by 1%, a large perturbation in paleoclimate terms. During 11-year cycles the sun changes by less than 0.1% and even that is detectable in the temperature. Just realizing this helps you to put it in perspective.

Proof is for mathematics. Science explains what we see in terms of basic building blocks.

You don’t seem to have a good grasp of what science is about. Every scientific hypothesis explains things, yet most end up being wrong. To distinguish between competing hypotheses we need evidence that disproves one of them, so we expend our time devising clever experiments and tests that will disprove every reasonable alternative explanation, and that will reinforce our hypothesis.

In this case it is the earth’s energy budget and the physics of greenhouse gases which explain why the earth has its current temperature and how the changing balance changes it.

The earth’s energy budget is not well known as it is about measuring a tiny variation in a very large magnitude, and its variations are compatible with multiple hypotheses about how it is maintained. The physics of greenhouse gases stops very short of explaining why the earth has its current temperature. To get there a lot of feedbacks and fudge numbers like aerosol forcing, that are unknown, have to be introduced. While the physics of greenhouse gases is well known, all the rest is almost completely unknown.

You need to start with AR5 WG1 and say what you disagree with there.

No, because it is not a question of disagreeing. I find the CO2 hypothesis reasonable, just not very well supported on evidence. To get to alarming levels almost all or even more than all observed warming for the 1950-2010 period has to be attributed to greenhouse gases, and that is a serious problem, because we know climate change has been taking place all the time. It is not reasonable that it just stopped in 1950. The alternative hypothesis, that CO2 is not the main control of temperatures, fits a lot better with paleo evidence, and has clearly not been disproved.

doubling it is like increasing the solar strength by 1%

More of those statements that you make like they have been demonstrated, when you really have no evidence to back them up. Looks to me that you are not talking science but your belief system.

You keep claiming things are not understood, when it is you that don’t understand them. There is enough evidence that the science is correctly accounting for why the earth is 33 C warmer because of GHGs. Understanding this much is important, but you claim it is not understood, but that is just you projecting. This seems to be a common flaw in skeptics that just because they don’t understand, and don’t seem to even be trying very hard to, nobody understands. Attribution since 1950 is easily explained as 100% GHGs with a two-step argument, but you won’t accept that even if I give it. Skeptics are just short of the knowledge they need to make a judgement, but that doesn’t stop them saying no one knows, as though that is what they truly believe.

There is enough evidence that the science is correctly accounting for why the earth is 33 C warmer because of GHGs. Understanding this much is important, but you claim it is not understood, but that is just you projecting.

Most people don’t know how science works, and the difference between something that has been demonstrated and something that is just hypothesized. I have tried to explain you that the jump from CO2 physics to explaining all warming in terms of anthropogenic emissions rests in suppositions and assumptions about feedbacks that are not well known, like water, ice albedo, and clouds, and on values like aerosol forcing that are not well known. This is really simple but you have a problem with it, because you don’t understand science, so you just trust it and in a belief system you don’t distinguish between fact and hypothesis, so everything becomes a fact.

Attribution since 1950 is easily explained as 100% GHGs with a two-step argument

Of course it is easily explained, but what you fail to see is that scientists could as easily explain the opposite. That explaining a phenomenon is not the same as demonstrating that the explanation is the correct one.

Skeptics are just short of the knowledge they need to make a judgement

That’s probably true of most people at both sides of the issue. You clearly display a lack of knowledge of what parts of the hypothesis are supported by evidence and what parts lack that support. You erroneously assume that everything is solid as rock. It is not.

I would like to see someone explaining the opposite because then I can show them where their argument fails to fit the observable facts.

That’s actually quite easy considering how little we know about how the climate works.
For example. Let’s say that CO2 produces only 40% of the observed warming (i.e. climate sensitivity of only 1.2). The residual 60% of observed warming can be easily assigned to natural processes. The warming is coming from a decrease in the Equator-polar temperature gradient, the expansion of the Haley cells, and contraction of polar cells due to the ongoing recovery from the LIA extremes. This also has important feedbacks in changes of cloud cover and wind intensity. The decrease in volcanic activity also helps. This has been modelled several times. So we do have alternative explanations to the CO2 hypothesis.
When the warming stops and it becomes evident that the CO2 hypothesis can only account for part of the warming, these alternative hypotheses will come to the forefront of scientific research for their higher capacity to explain what is going on.

The problem with that is (a) that the land is warming twice as fast as the oceans for the last 30 years, and (b) the positive imbalance says that the warming is from a forcing term and not an internal redistribution of energy. What else do you have given these extra facts to fit?

I don’t understand why you think that is determinant for the hypothesis. The land doesn’t store heat, and the atmosphere stores very little heat. Most of the land warming that you speak about is coming from the Arctic and high latitudes at both hemispheres,

and most of it outside of the melting season as we all know.

But we also know that Arctic and high latitudes air is very cold and therefore has low humidity, which means that the temperature difference might be high, but the heat content difference is not so high.

I also don’t see the problem with the warming observed not being from internal redistribution. The main thing is that we don’t know what is producing the warming. We have an attribution problem that lots of scientists are willing to ignore, and that has never been a good scientific approach.

The planet is near the coldest it has been in the past 650 Ma. According to Scotese (2016), the average temperature during that time was 7C warmer than now. And guess what? Life thrived through most of that time. These facts do not support the contention that global warming will be dangerous or catastrophic.

No. We are at about the coldest point in the last few millennia. At the resolution available for the Holocene global temperature reconstructions, about few hundred years is one point or two.

At higher resolutions, most local holocene temperature proxies show that the warming during the last few hundred years is NOT unprecedented and that the LIA trough is the lowest point. Furthermore, only the warming since ~1950 is claimed to be partly anthropogenic.

Climate changes abruptly. Always has always will. Life thrived during rapid warmings in the past. Warming from the severe coldhouse phase we are currently in would probably be beneficial, as it has been for the past 100 years.

Extinctions occur when the changes are the kind we are headed for. Habitats disappear. Ecosystems are disrupted. That’s how it goes.

We don’t know what climate we are headed for. A lot of people assume that the changes they have experienced are going to continue indefinitely into the future. That’s call extrapolating, and is really a bad prognosticating technique.

Well over 90% of the habitats that have disappeared and ecosystems that have been disrupted are the direct result of human activities and pollution. If that is really your worry, you are in the wrong cause. The fact that we are growing about 70 million people every year is putting a lot of pressure on natural ecosystems. CO2 is actually helping by increasing ecosystem productivity by increasing winter temperatures, growing season length, and plant productivity.

We have had 2 W/m2 of forcing. Projections based on BAU emissions get us up to 6 W/m2 by 2100. You can claim that won’t have much effect only by dismissing the science. These magnitudes are comparable with what is needed to remove the last ice we have.

It is calculated from assumptions and suppositions that we have had 2 W/m2 of forcing. The real value is unknown.

Projections based on BAU emissions get us up to 6 W/m2 by 2100.

Projections coming from models based on assumptions and suppositions and all things being equal about phenomena poorly understood get us up to 6 W/m2 by 2100. We shouldn’t place too much value on those projections.

You can claim that won’t have much effect only by dismissing the science.

I don’t dismiss the science. I am 100% pro-science. Heck I am a scientist with articles in journals like “Science”. I have dedicated my life to science. Your problem is that I do understand science and what is supported by evidence or not, and you don’t.

If you understand science, you understand forcing and the greenhouse effect, and the way climate in the past is consistent with forcing changes from the greenhouse gas changes and albedo, volcanic and solar changes, and how physics has been used to derive it quantitatively since Arrhenius. But it appears you are dismissing 90% of this for no good reason. Or, maybe you’re not outright dismissing it, but just phrasing your skepticism as if you do for argument’s sake. Be more specific about what of that you have dismissed, so we know where we differ.

If you understand science, you understand forcing and the greenhouse effect

Yes I do.

But it appears you are dismissing 90% of this for no good reason. Or, maybe you’re not outright dismissing it, but just phrasing your skepticism as if you do for argument’s sake.

You have to understand how science works. We have principles on which the entire foundation of science rests. We know these principles to be correct because otherwise we do not have science. We call them laws. Their value might change slightly but the law cannot be modified. Then we have explanations that are supported by a huge amount of evidence from multiple disciplines. We call them theories. They can be changed and perfected as knowledge evolves. The theory of evolution has incorporated the genetics and many special cases like group selection, transposable elements, so on. Newton’s gravitational theory is now known to be a special case of Einstein’s relativity. Theories do change but they are extremely unlikely to be demonstrated wrong in great part, not so much in some details. Then we have explanations that are supported in part but not all the evidence. And there are alternative explanations that have not been discarded yet. We call them hypotheses. They can be completely changed or discarded without any harm for science, and usually they are. Our level of confidence on hypotheses has to be much lower. The CO2 hypothesis states that CO2 is the most important factor in determining the climate of the earth, and that more than 100% of the observed warming since 1950 can be attributed exclusively to CO2. Then we have explanations that are supported by a little bit of evidence. We call them conjectures. Like that the Younger Dryas was started by a celestial impact, or that interglacials are determined by dust. Even though most neutral scientists consider conjectures to be highly improbable, they are still published because they are considered worthy of being discussed in the field.

I don’t know how many scientists support the CO2 hypothesis, but for the sake of the argument let’s say it is 97%. This is because they have not checked the evidence. It takes years of very hard effort to review the evidence of a subfield, so all scientists are like me and outside their own subfield they trust the conclusions reached by the most prominent scientists in other subfields. So I used to believe in the CO2 hypothesis as most scientists do. But I have a blog, and in my blog I decided to talk to people about the dangers of global warming. How ironic. I started to review the evidence and I found none. The dangers are based on pure speculation and exaggeration, and completely outside of experimental evidence. Then I continued digging. The basic principles are obviously correct, as I expected, but there are a lot of unknowns and alternatives that are not being properly explored for something so important. Then I saw a lot of bad science being published as propaganda and unacceptable behavior. These are the trademarks of something fishy going on. Then I checked paleoclimatology. Despite the rewriting and reinterpretation tht is being carried on, paleoclimatology supports that CO2 is a second order factor in the determination of earth’s temperature. Hell, from wanting to write in favor of global warming, I was forced to write against it compelled by evidence, despite being a very strong conservationist. That’s too bad. Scientific consensus has been wrong many times before. The sooner we fix that the better for science.

You better have some doubts yourself about what you defend. You have not considered the possibility of being wrong on this. I tell you from experience because I was wrong too.

You seem to be dismissing AGW as not have a chance of being right despite it fitting all the data and paleoclimate. It is in the category you describe as “Then we have explanations that are supported by a huge amount of evidence from multiple disciplines. We call them theories.”
The earth’s temperature has shot up 1 C at the same time as we added 2 W/m2 of CO2 forcing, both very unusual events in the measured record. Even small solar forcing changes of 0.1 W/m2 are noticed in the temperature record, yet you dismiss that 2 W/m2 can show up as 1 C despite there being a lot of physics to explain how it does. It is your complete dismissal of this possibility that puts you at odds with the scientists who study this stuff and are just refining it.

You seem to be dismissing AGW as not have a chance of being right despite it fitting all the data and paleoclimate.

I have not said that. Every hypothesis has a chance of being correct until evidence is found that falsifies it. Fitting the known evidence is necessary but not sufficient for every hypothesis. And the CO2 hypothesis might be 40% correct and I would not have a problem with that. You would.

The CO2 hypothesis is not a theory because it does not explain all evidence, because it is not supported by evidence from other scientific disciplines, like biology. Biology supports the warming, but not that it is due to CO2. And because there are alternative hypotheses that have not been discarded.

The earth’s temperature has shot up 1 C at the same time as we added 2 W/m2 of CO2 forcing

Several things are not correct in that short phrase. The amount of warming is unclear, and probably in the 0.6-0.8°C range. The amount of forcing coming from CO2 is unknown since we do not know its climate sensitivity. And the increase in temperatures and the increase in CO2 did not occur at the same time. The world has been warming since about 1840, while the increase in CO2 really took off after 1950.

I do not dismiss the warming contribution from CO2. You keep putting words in my mouth that I have not said. This is really an indication that you don’t know how to respond to me and need a strawman for your prepared lines. I am convinced CO2 has contributed to the warming and I defend so and am called regularly a warmist at WUWT. I just don’t see any evidence that over 100% of the warming since 1950 has been due to GHG forcing, or that we are in any danger from catastrophic consequences due to human caused warming. The evidence is simply not there.

The positive imbalance means that the forcing exceeds the warming. The forcing is dominated by GHGs. How, from these facts, can it not be that the GHGs forcing exceeds the warming we have had so far and that there is more warming in the pipeline due to the GHG increase that we have already had? If emissions stopped today, warming would continue until the imbalance is removed. It is counterfactual to argue otherwise.

Thanks for another interesting post.
This is a bit off topic but a personal experience gave me an appreciation for the importance of insolation. This winter I was walking off a Florida beach and used some wooden stairs. The stairs had 2″ by 6″ blue wooden hand railings. The railing was alternatively at a diagonal and then horizontal. The diagonal railing had the sun rays perpendicular to the surface. The horizontal railing had the sun rays striking at an oblique angle.
As I touched the railing at different points I found a remarkable difference in their surface temperature. It was quite significant with one being cool the other hot. Just inches separating them with same ambient air temperature and yet the perpendicular sun rays made such a difference.
It made me realize how insolation can affect climate in such a great way.

JimDWe have had 2 W/m2 of forcing. Projections based on BAU emissions get us up to 6 W/m2 by 2100. You can claim that won’t have much effect only by dismissing the science. These magnitudes are comparable with what is needed to remove the last ice we have.

Yes that 2-6 W/m2 will hit us – in 6500 years. We all need to reflect on the profound implications of figure 35, that insolation from obliquity forces climate with a 6500 year delay since climate comes to us from and through the oceans. Climate is oceanography.

This means that all the “climate change” that will happen is already in the pipeline on its way to us, from solar forcing in deep prehistory >6000 years ago. I don’t think even Ruddiman would argue for any anthropogenic effect back then. As Bon Dylan would have put it there’s a “slow train coming”. Part of this is glacial inception which Javier showed us on an earlier post will likely happen in about 2000 years. That’s locked in – nothing we add to the atmosphere now will change that.

In 6000 years time as Canadians and Scandinavians queue at embassies in warm countries, we may be glad 😁 of that 2-6 W/m2 which will finally come due.

Policy can be based on the central values that also best fits the warming we have seen so far. They have said that the most likely attribution is 100%. Go with that, and don’t dismiss it. It could equally be better or worse than that.

Jim D:
If 90% of the warmth is going into the oceans, and some claim that and I’d say it’s likely true, to me that’s a claim of material lag recently. Unless this is some odd anomoly it might just be the natural state of long term ocean warming as in a recovery from the little ice age. It may be that the CO2 is trapping the warmth in the ocean. I accept that, pushing the warmth away from the atmosphere and telling it to warm oceans to great depth instead.

“Below the sea surface, historical measurements of temperature are far sparser, and the warming is more gradual, about 0.01°C per decade at 1,000 meters.”

“According to the theory, land relative humidity changes
and the land-ocean contrast in the control climate contribute
equally to the tropical warming contrast, while ocean relative humidity changes make a smaller (but also positive) contribution. Intermodel scatter in the tropical warming contrast is primarily linked to land relative humidity changes. These results emphasize the need to better constrain land relative humidity changes in model simulations,
and they are also relevant for changes in heat stress over
land.” Citation: Byrne, M. P., and P. A. O’Gorman (2013), Link
between land-ocean warming contrast and surface relative humidities in simulations with coupled climate models, Geophys. Res.
Lett., 40, 5223–5227, doi:10.1002/grl.50971.

It says that land surface temperature increases are influenced by surface aridity.

Indeed the land will dry out as it arms faster than the ocean because its moisture is provided by the ocean and cooler ocean, wamer land, means lower humidity over land, less clouds, more heating, hotter land. It is a positive feedback that reinforces the differential warming.

It’s not a feedback – it is just a change in the proportions of latent and sensible heat flux at the surface. Thermometers measure more warming because there is less latent heat flux. It is in other words – not real.

The omnipresent and hyperactive green conscience of Climate Etc. gave it his best shot and Sr. Javier shot him down. We have seen it happen many times, in Oh! so many years. But this one seems somehow more succinct and elegant. Nice work, Sr. Javier.

“Round like a circle in a spiral, like a wheel within a wheel
Never ending or beginning on an ever spinning reel
Like a snowball down a mountain, or a carnival balloon
Like a carousel that’s turning running rings around the moon”

“According to the theory, land relative humidity changes
and the land-ocean contrast in the control climate contribute
equally to the tropical warming contrast, while ocean relative humidity changes make a smaller (but also positive) contribution. Intermodel scatter in the tropical warming contrast is primarily linked to land relative humidity changes. These results emphasize the need to better constrain land relative humidity changes in model simulations,
and they are also relevant for changes in heat stress over
land.” Citation: Byrne, M. P., and P. A. O’Gorman (2013), Link
between land-ocean warming contrast and surface relative humidities in simulations with coupled climate models, Geophys. Res.
Lett., 40, 5223–5227, doi:10.1002/grl.50971.

It says that land surface temperature increases are influenced by surface aridity.

“The heat content of surface air (i.e.,z right above ground level, so that z = 0 can be assumed) can be expressed as:

H = CPT + Lq

where Cp is the specific heat of air at constant pressure,T is the air temperature, L is the latent heat of vaporization, and q is the specific humidity [Haltiner and Williams, 1980] .The quantity, H, is called moist static energy and can be expressed in units of Joules kg’.

The surface dry static energy can be written as S
= CPT.

Surface air temperature trends that have been reported monitor S.The monitoring of H, however, is the more appropriate metric to assess surface global warming.”

In Joules the oceans are winning. About 250 for the ocean and about 5 for the atmosphere. Let’s say for the time being I go along with we caused all the warming in the atmosphere. So the total is 5 plus 250 and I guess we did that assuming no net cloud gain/loss budget change. We’d also have no ocean recovery from the little ice age as we caused the oceans to warm.

The “LIA recovery” is a myth. There is no mechanism for it. Without the CO2 increase, temperatures would be more like in 1750 because of the Milankovitch trend being downwards. So all this extra energy you see is from the GHG increase.

In the presence of strong forcing the land’s warming will outpace the ocean by virtue of lower thermal inertia. Are you arguing against that happening? The divergence of warming is what is expected in the present conditions as forcing increases by 0.3 W/m2 per decade, which is fast by any standards.

Jimmy seems a bit like the proverbial goldfish in a bowl, It is perversely fascinating to watch.

“According to the theory, land relative humidity changes
and the land-ocean contrast in the control climate contribute
equally to the tropical warming contrast, while ocean relative humidity changes make a smaller (but also positive) contribution. Intermodel scatter in the tropical warming contrast is primarily linked to land relative humidity changes. These results emphasize the need to better constrain land relative humidity changes in model simulations,
and they are also relevant for changes in heat stress over
land.” Citation: Byrne, M. P., and P. A. O’Gorman (2013), Link
between land-ocean warming contrast and surface relative humidities in simulations with coupled climate models, Geophys. Res.
Lett., 40, 5223–5227, doi:10.1002/grl.50971.

It says that land surface temperature increases are influenced by surface aridity.

I know better than to argue with skeptics about model results, so no matter how many modeling papers you and RIE throw at me, I won’t be drawn. You don’t trust models, and it is pointless to have that discussion. I stick to observations.

So you trust the models that say you are wrong yet still insist you are right despite those models but you don’t wish to discuss it because I don’t trust the models. That certainly makes sense, or it least it will if I drink enough.

“Before we started burning fossil fuels, Earth’s oceans had been cooling for almost 2,000 years.
The primary cause for this cooling was a cluster of volcanic eruptions that suppressed global temperatures by blocking out sunlight.”

http://sciencenordic.com/modern-industrialisation-killed-ocean-cooling
Recovery from the LIA is a myth.
I don’t want the oceans to keep cooling. We’d be growing wheat in MN instead of corn and soybeans. I think it’s fair to say that things had been cooling for around 1800 years before the LIA ended. Michael Mann’s hockey stick shaft was slowly falling. We did solve that problem by burning stuff. Was it normal to reach the LIA and stay there? The thing to do back then was to cut down forests and burn coal. That would have been the correct policy, if we had known. In the plot, what is the equilibrium temperature? I could be lower where the data spends most of its time going? Or it could be oscillating around some mean. Now expand the plot to 6,000 years and figure that equilibrium. I am sensing from you that the equilibrium is lower and materially lower then even 1950. I might be that we got things right up until 1950 and then we should have stopped. We gave a measured response and then we stopped. Except we didn’t stop as just wanted cheap energy and a 40 hour workweek and color TVs. And A/C too.

Above a brought up 5 atmosphere compared to 250 oceans warming. I can accept 5 for the sake of argument, but 250? That’s us. That we can so control the 4 kilometers of average ocean with the atmosphere. Maybe we can agree we control just ½ of the oceans temperatures. With our atmosphere that spends a lot of time radiating to the TOA and back into the ocean.

If we had a joules based climate sensitivity, using 5 atmosphere and 250 oceans warming, it would be about 50 times more. For every 1 joule we trap in the atmosphere long term, we trap 50 in the oceans.

You can work out the total Joules of anthropogenic forcing. Let’s say 1 W/m2 for a century as a rough guess. That is 3.e9 J/m2. That is about 1.5e24 J over the surface of the earth, so, yes, that ocean warming does need a lot of energy, and, yes, we have supplied it.

Regarding the optimal CO2 value, there is a case to be made for 350 ppm. See 350.org. They talk about a safe operating space for earth’s CO2 levels, and they also recognize that the 280 ppm at the LIA wasn’t ideal.

Jim D, It doesn’t matter what I think. You either think they have value or you don’t. Simply dismissing them when they don’t match your preconceptions indicates you don’t think they have any value. Everyone that touts the models as pretty good turns around and treat them as worthless when it suits them. I do enjoy your dancing though.

It matters why you trust the model results you show. Each model study is done a different way. I am not going to read whether what they did is valid to me. You can tell me why you are so convinced, and I can judge it that way. For a model study to be relevant, we have to see whether they have represented the forcing realistically to be able check results against observations. That would be a validation check. At least with observations, we know what we are talking about.

BTW, I looked at the two papers you linked, and in one case they detrended the results, so they were not talking about the response to the forced change, only internal variability, and in the second the land temperature when unforced had a completely wrong pattern of warming due to the lack of the CO2 effect. Just adding ocean warming gives a lot of land warming via the water vapor feedback, but is otherwise inadequate to explain the pattern, especially the maximum warming over the northern continents. In both cases their conclusions were very sensitive to the model, and need to be taken with a grain of salt because of that.

I don’t have to be religious to argue with a preacher what the verses of the Bible say. I don’t have to be religious to argue with a global warming cultist what the models say.

Taking internal variability and showing the proportion of change in response to something that shouldn’t be external forcing for land and ocean remains the same shows a direct contradiction to what you have been chanting.

I’m glad you appreciate the power of observations. That is why I showed you previously, several times probably, how nicely the pattern of emerging temperatures follows ocean circulation. Observations aren’t on your side either.

The models typically don’t show enough temperature change in the N Hemisphere to changes in ocean circulation so that isn’t something peculiar in this case. I would consider it a common flaw unless you can show one that comes up with a pattern that makes sense. Hint: a pattern that doesn’t affect the N Atlantic and the Arctic the most makes no sense.

What those papers show is the power of the greenhouse effect of the water vapor by itself to warm the globe, and especially the land that responds fast. What you are looking at is the H2O greenhouse effect in action, which points to the importance of the water vapor feedback as a component of the total. The missing high-latitude warming is the part that the CO2 would have been expected to provide, but all they did is effectively add the water vapor from future SST warming without the CO2. An interesting academic exercise, but of limited applicability to the forcing we actually have from both H2O and CO2. This is why I don’t read too much into these model exercises.

The model exercise shows the models think it is the oceans primarily responsible for the land warming and at least one of the two specifically states that it is not direct radiative forcing that is causing the land to warm faster. That is not what you think so the exercise was to show you that your bible and your sermon had disagreements.

It is radiative forcing from the water vapor increase. The land responds quickly to that. Both refer to increased downward longwave radiation from the water vapor increase and a positive feedback from that over the land area.

Jim D, water vapor from increased SSTs. I’m sure you must remember that the models also show increasing ocean heat transport causes a dynamic increase in water vapor above and beyond that expected from just a temperature increase. The bottom line is these models dispute what you have been saying. That’s fine that you have no trust in the models, there are reasons to doubt their veracity, but you need to admit it so you can join the rest of us skeptics in saying there are important questions that need answering and not just some fine tuning details.

I think the dominant role of the water vapor greenhouse feedback in this process, even without any added CO2 in these rather specialized model tests, attests to the weakness of the low-sensitivity argument that relies on water vapor not adding much. To me, it is no surprise that the greenhouse effect of added water vapor is so crucial in amplifying the land warming so on this the model is just doing as anyone expects from physics. The significant greenhouse effect of increased water vapor goes back to Arrhenius, so this is just more backing for his idea.

If LW radiation slows ocean heat transport, and the models say it does, that is a negative feedback and it could have a very low sensitivity. You take the smallest kernel off the cob and try to make an ear of corn out of it.

You can check the papers you quoted to find that they attribute the land warming to the extra downward longwave from the added water vapor. It actually has nothing to do with the ocean for which they just specify the surface temperature at the outset, so I am now not sure what you are reading.

OMG Jim, one is titled “Oceanic Influences on Recent Continental Warming” and the other is titled “The Ocean’s Role in Continental Climate Variability and Change”. Did you not make it as far as the titles of the papers at least?

Neither paper makes reference to the ocean heat transport nor your purported longwave effect on it. Your point had no relevance to the papers at all. The simple reason was that they did not even have any ocean heat transport in their models. This is the problem I have with talking to skeptics about models. They don’t know about the models in the first place, and then draw completely wrong conclusions as a result. It just proves to be a waste of my time as I said at the outset. Move on.

Come on Steve, you and I both know it wouldn’t have made any difference if he had, he totally lacks the knowledge and understanding of the subject to have derived anything from reading them anyway.

He’s just clown dancing, stringing you along to provoke a reaction, he has no interest in a serious debate, it isn’t even clear that he could care less about AGW – or any other aspect of the environment either, come to that.

If ocean surface warming is gradual, the land response will be gradual, but if warming arises out of nonlinear interactions between the ocean and atmosphere (involving land as per the coupled transport process above) nonlinear warming on land would follow almost immediately, perhaps driven by the processes described by Reid and Beaugrand (2012). Under this hypothesis, decadal climate regime change arising out of ocean‐ atmosphere interactions is capable of producing step changes in mean sea surface temperature. Consequently, these step changes could be transmitted to adjacent continental areas and/or though teleconnections. The atmosphere has no heat storage memory but the ocean does. If the added heat energy trapped by anthropogenic greenhouse gases follows the same path as natural heat energy trapped by naturally occurring greenhouse gases, the interaction of external forcing with internal variability is a logical result.

You should have said the papers had nothing to do with my last comment instead of nothing to do with the oceans. They also didn’t have anything to do with indicating a high sensitivity which is what I was responding to.

They indicated that the increased water vapor greenhouse effect is large, which is a killer blow to low sensitivity arguments. Of course, now you’ll say this is just a model, which is why I say it is a waste of time for me to discuss models with skeptics, even those who keep quoting modeling papers.

Direct radiative forcing is only causing 14% of the land warming according to one paper. That is the direct effect and implies a very low sensitivity of about 14% that which you have been claiming. They didn’t use the models to warm the oceans as you so astutely pointed out earlier so you can’t claim it was due to CO2 in the model and even if you could there would be some explaining to do as to why the direct effect is so small. They are not pointing to a high sensitivity at all.

No, this is just the water vapor feedback to the warming that they say warms the land with its own positive feedback. It is important to see how much that does. You can add CO2 on top of that, but they did not do it that way. The warming you see over land is just from increasing water vapor. This is the point.

JCH:
Is there a change of position on your part? Double plus good link.
“The atmosphere has no heat storage memory but the ocean does.”
It’s not expected to store it. It does remember it has more CO2 in it, so it remembers to retain it longer. We can say that’s still storage, just weak storage. The oceans remember the climate from centuries ago. The Antarctic land ice remembers further back with its mass. The land temperatures depend on what the ocean SST is and how much volume of the near surface atmosphere crosses from oceans to land.

“Uncoupling transport between land and ocean leads to little warming for either, showing it is the coupled relationship between the two that is important (Lambert et al., 2011).”

Why? The oceans if they don’t transport, just reabsorbs the warmth with their massive thermal capacity or it goes TOA. And the atmosphere over land doesn’t even have the storage to hold onto the additional warmth after raising the average temperature something small but still material and real. It is fed by ocean warmth for sustained material increases.

Now back to my rigid jet stream theory. West to East flow from the Pacific to the Americas. From the Atlantic to the Europe and Africa. The rigid jet is a warming planet. With good traction in the hemisphere’s Winter. The wavy jet loses West to East transport. Tsonis 2007 talked about a wave 2 and wave 3 anomaly at the beginning of that paper which I interpreted a rigid (2) and wavy (3) jet stream.

“Atmospheric model simulations of the last half-century with prescribed observed ocean temperature changes, but without prescribed GHG changes, account for most of the land warming”

They are comparing observed SSTs to observed land warming and discovered matching the SSTs in the model to observations can cause almost all the observed land warming. There is no adding on to the observed temperatures. They are observations not model results. Your only argument would have to be that the oceans were causing way too much land warming in these models if you wish to keep claiming a high sensitivity to CO2.

“This is supported by observations on land where the overpassing air mass takes on the characteristics of the underlying surface, achieving energy balance within a 300 m distance (Morton, 1983). When passing from land to water, this will see all of the available heat energy taken up by water if the temperature of the air mass exceeds that of water (Morton, 1983, 1986), with the temperature of the overpassing air mass reaching equilibrium with the water beneath within a very short time.”
– Jones and Ricketts
If CO2 can’t warm the the oceans, where did the heat energy go? This where they those people get it wrong. It’s a good thing.

The exercise is not imitating nature, so they don’t disprove that forcing causes the land to warm faster than the ocean, having deliberately removed that factor from their experiment. The ocean lags the land in reality, so that has to be explained first. External forcing explains it.

Jim D:
I must disagree. Because the atmosphere over land has little thermal inertia, it must get sustain from elsewhere. The TOA emission never sleeps and can deplete that which doesn’t have large reserves. Wind from the oceans will have greater humidity on average that will help with additional water vapor which may explain part of the difference you point out.

Here’s part of not having inertia. A more rapid speed up and slow down. Which is what land temperatures do. Compared to the oceans they are agile. Agile is fed with high amounts of inputs and without them you don’t get much. Put jet fuel into a fighter. Amazing. No jet fuel, looks nice doesn’t do anything.

I think they said they decoupled the oceans from the land. They got very little, showing to me land’s true attributes. It lives off of the oceans inputs. When we think of good joules uptake, that’s the oceans. Let’s say in Summer, the land warms faster during a day. How much of that can it hang onto? Since it can’t hang onto it, it radiates it. While the ocean’s have shown their ability to hang onto things. Atmosphere over land is like a spendthrift. Yes it’s warm, and you can’t hang on to the joules, they’ll be gone soon. Since over land they can’t be absorbed by the average 4 kilometer depth of ocean, I wonder where they go? The land keeps re-emitting them while the oceans at times will do less of that if there is long term storage occurring at a certain time.

Take a look at the graph I posted. Interpret that. The forcing is causing warming, and the land is responding faster. It is analogous to how the change to summer warms the land faster. The rising greenhouse effect is a multidecadal analogy to the approach of summer. Sure, if the forcing trend reversed, the land would dip in temperature first. There is a period after 1940 where you can see that happening too, but now the forcing has been steadily rising for many decades, and the relative thermal response is not surprising.

The observations show the lag. It is quite clear. Don’t you see it? The land starts warming first and fastest. Hard to explain that as the ocean starting it. The forcing started it, which is only a complete surprise to you. Since 1980 the forcing has change by about 1 W/m2 which is large enough to account for what you see. It is also a major inconvenience to skeptics that CRUTEM4 (land) so clearly leads the AMO. This all points to this large external forcing as the driver.

If CO2 can’t warm the the oceans, where did the heat energy go? This where they those people get it wrong. It’s a good thing. …

They’re not getting anything wrong, and it’s not a good thing. And no, I have not changed positions on anything. Jones pretty much agrees with what I have been saying here for years, though the verbiage “heat leaves the oceans and warms the land” is, imo, an incomplete and unsatisfactory way to put it.

No Jim D, the lag is not clear. The difference in amplitude is clear. The models recreated that difference in amplitude just by changing SSTs. Yes, the oceans warmed the land more than they themselves warmed.

If I can’t even convince you with observations, there is no hope for you. What would it take to show you that the ocean warming lags the land and remains slower than it, or that in the presence of so much external forcing this is just as expected?

From a causality perspective, it is hard for the land to warm before the SST by any mechanism you envisage for the SST changing the land temperature. Clearly the land is responding to the large forcing change, not the ocean, and the ocean is also responding to that forcing change which is why its OHC has risen so much at the same time. Also the land has warmed twice as much as the ocean in the last 30 years and the temperatures continue to diverge. Most of the land warming is in interior continents far from coastlines.

What you have is cognitive dissonance. The observations are just as would be expected under strong external forcing with the land response leading that of the oceans. It’s thermal inertia in action. No one is surprised.

I don’t recall ever arguing the climate models had to be right but I do remember you saying they were because they were based on physics after all. I’d say your arguing they can do the impossible now makes you the one with the cognitive dissonance, that is unless you now think they are crap, do you?

Climate models being able to represent the warming rate so far are evidence that the physics of AGW is right. I prefer to go with physics like the energy balance and observations, but models can be used to support this view too. You can also use models to do other things, like seeing what happens if you warm the ocean and don’t add CO2. It is not what happened in nature, but you can do the model experiment and you have to be careful about how you interpret it because of that deviation. The first paper you listed did a more natural doubled CO2 experiment and the land warmed by 5 K, the ocean by 3 K, but you don’t mention that one.

Jim, it’s sort of a basic principle of arguing that using sources the other person trusts is the best way to convince them to change their position. For instance if I wanted to support a point and I had a choice between Judith or Mann to pick as a reference and I were arguing with you then I would use the Mann reference. I suspect you have now changed your position and will no longer be saying that it is impossible for the oceans to have caused the warming since your only alternative is to dismiss models as having any usefulness what-so-ever. If I had made my own arguments you would never have been faced with having to pick which of your positions you would be forced to change. You would have just kept saying it was impossible until Hell froze over and for a while I thought you might even if it meant dismissing models as useful.

The oceans didn’t cause the warming. What are you talking about? The forcing caused the warming of both the oceans and the land. You have done nothing to change that view. Maybe next time you quote model results, you should find one that isn’t showing that much sensitivity to CO2 doubling because it kind of defeats your point when doubling CO2 warms the land by 5 degrees, and they also show that the strength of the water vapor feedback is critical to that warming, which is where the ocean comes in.

Let’s try to figure this out. Ocean SST is X in a square kilometer 10 kilometers from the coast shore. The sun comes up and that goes to X + 1 C. The wind then blows it inland. It blows 0.5 C inland which is now shown as plus 0.5 C land. The square kilometer kept 0.5 C for itself. We say they warm at the same rate, even though the ocean warmed and then cooled and supplied the land with the increase.

Say the ocean kept 0.33 C for itself and sent 0.67 C inland. That’s your plot. SSTs are at the interface. Like a vehicle’s radiator. You could plot the water temperature in the water jacket next to the cylinders. After the engine warms, no change on average. You could then measure the surrounding air temperature and say the source is not the cylinders, it’s something else.

It would seem that for life to have developed on Earth, the oceans do cool more than before when they are warmed.

According to this paper the main contribution of the ocean to the land warming was via adding water vapor and its greenhouse effect. The direct transport of heat would not be balanced and sustained against radiative cooling to space, but a greenhouse effect would be. The key to a lasting effect is changing the greenhouse gases in the column.

JCH:
I think it’s a good thing. 90% goes into the oceans. The warming is in the pipeline and that pipeline is about a century long. And the more CO2 we add, the longer the pipeline becomes. The warmer the atmosphere becomes the greater the differential pushing joules back into the oceans.

People want to sequester carbon. The oceans sequester joules.

“If we continue to use the temporary slowed surface warming as an excuse to delay climate action, we’ll regret that decision when the surface warming kicks in with a vengeance.”
– Dana Nuccitelli
And the joules shall come out of the oceans because they increased so fast they are changing. They are fed up with being in the oceans and want to get out. Never mind the other joules trapped there for thousands of years, these are vengeful joules, like Neptune enraged.

Jim D:
Evaporation indicates cooling as far as I know.
Pot of boiling water. Temperature is constant. The pot is perfectly insulated except for its top. Electric element heats the water. It is the source while remaining at 100 C. As the unvented air in a 10 X 10 X 10 room warms it pushes back into the pot. The electricity can then be dialed back some.

The atmosphere is a plexiglass enclosure. The land is something that will absorb some warmth but hold it for only a short time. The Sun is cycled on and off to see both day and night activity. During the day, the water captures joules and releases some of them. It increases humidity levels. Joules movement is from Land to Water during the day as the Water lags the Land. During night the joules move from Water to Land warming it. At night the sources of joules are the Water warmed during the day plus any warmth remaining from the prior day plus a small contribution from the cooling Land. The Land is a minor source for Water warming. Water being better able to absorb and store joules is the major source for the system.

Now add CO2.

The Land joules have their old path, into the Water. The land can punch more into the Water as less is lost to the TOA. The Water will lose less to the Atmosphere during sunny days. The water has now warmed because of the CO2. Its SW absorption is the same. At first it emits less because of the CO2, but then it has more to emit which does it, while having greater storage. The water has more joules than before and will emit those to the Land for a longer time each night. CO2 has lowered TOA loss until the new warmer equilibrium is reached. Each night the Water tries to reach equilbrium with the Land which has little storage so it’s a waypoint on the way to the TOA. It is the Water warming the Land more than before with the help of CO2.

The CO2 also helps the land warm directly, as does the extra water vapor from the warmer ocean, and it turns out that this is the effect that sustains the land warmth. Also warmer air holds more water vapor so there is the positive feedback from that too.

The way to sustain warmth is via an increased greenhouse gas. The warming of the ocean relies on the water vapor greenhouse effect to achieve this sustained effect. Without it, all the extra warming is just radiated to space because it is not balanced.

The argument was over whether or not the oceans could warm the land more than the oceans themselves warm regardless of what caused the oceans to warm. You said no, the models said yes. Everything you have been saying is nothing but obfuscation. We can move on to other topics once you state if you were wrong or the models are crap.

They can because the water vapor effect amplifies it over the land while the ocean has no such amplification because its temperature is kept fixed in those model runs. If the ocean was also allowed to warm, all bets are off which warms more in the long run because the water vapor can provide a feedback to the initial warming. One thing that does happen, however, is that the land warms faster in response to forcing than the ocean would if it was allowed to respond, and that is just thermal inertia.

They warmed the oceans manually to match historical records. That is warming. They did do a model exercise where they kept the SSTs constant and doubling CO2 in that model run warmed the land by only 0.6 C. Oceans rule.

Oh, and the water vapor thing. You do realize that they knew water vapor went up but how much warming it caused wasn’t specified and that they were just speculating. They also listed another possible reason or two and maybe I missed it but I don’t remember them mentioning the albedo changes if any. I suspect there must be albedo changes because that’s what happens when you increase SSTs using ocean heat transport and I see no reason to suspect a lack of albedo change regardless of the cause of the SST change. I suspect the only real difference between the manual adjustment run and what you would see in an ocean heat transport model run would be you would be missing the dynamical increase in water vapor.

You would miss the feedback to the ocean itself in this simplification. In this sense you don’t achieve the final balanced state because that part is restricted from happening. You only learn a limited amount from this type of test. They did a test where they just doubled the CO2 and that is more informative, but still lacks what happens to the ocean currents making the sea ice also uncertain.

Interesting. We get all those ice ages just erfore the Holocene thanks to the orbital changes of Milankovich. Here is my problem: these orbital changes are nothing new. They were the same in say, Cretaceous, as they were in Pleistocene. Will someone tell me who turned off the Cretaceous ice ages? (plate movements don’t count). Another thing: Anthony has an interesting climate shift story that goes back before the Holocene. He points out that climate change around Antarctica does have an influence on Australia;’s rainfall. And ties this to Antarctic ice sheet expanding about 14 million years ago. One of his commmenters (Bill Illis) then has some interesting maps showing the closure of the Panamanian Seaway. The final closure according to him was 15-12 MA ago. That fits with the time Antarctic ice sheet expanded. Is it possible that the two are related? Loss of the warm equatorial Pacific water that was pouring through the Seaway before it closed should have lowered the Atlantic ocean water temperature and perhaps start the Antarctic cooling in motion?

Nobody knows why ice ages like the Quaternary take place. There are several hypotheses. Some blame CO2, others tectonic changes, and yet others the crossing of galaxy arms by the solar system. What we do know is that it is extremely likely that orbital changes affect climate regardless of the planet being in an ice age or not. As the temperatures at the poles are always colder that at the equator, periods of high obliquity must always be warmer than periods of low obliquity.

Regarding the closure of the Panamanian Seaway, its dating is contentious, as it was a continuous process and not a sudden shift. So land mammals were the last to be allowed through. Plants made it through much earlier, and the communication between marine animals at both sides was cut somewhere in between. Recent geological data has questioned the previous calendar, but the experts clearly disagree. It seems very probable that it had an important climatic effect. But the effect itself is complicated. Without communication, water that evaporates in the Caribbean rains over the Pacific and this makes the Atlantic saltier and probably warmer. The effect is a more active thermohaline circulation, enhanced North Atlantic deep water formation and eventually more cold water upwelling at the Southern Ocean.

However in my opinion the most important factor in the freezing of Antarctica was the opening of the Drake Passage 20-40 million years ago. This allowed the formation of the circumpolar current that climatically isolates Antarctica. The result is that Antarctica has its own climate as if it was in a different planet.

Here is my problem: these orbital changes are nothing new. They were the same in say, Cretaceous, as they were in Pleistocene. Will someone tell me who turned off the Cretaceous ice ages? (plate movements don’t count).

Don’t confuse model temperature projections for modeling of mechanisms. In the first case the solution are dominated by nonlinear divergence caused by nonlinear core equations. The latter shows land aridity – from whatever source – causing the land/ocean temperature divergence. The letter is based on fundamental physics.

You should not confuse – either –
jimmy’s narratives with fundamental physics.

Today’s discussion or not.
1% of the total world energy production (includes gasoline, diesel fuel and others) is wind and solar. Assume a 100% ability to replace CO2. Assume hydro power was constant meaning a somewhat more than 1% impact on CO2 reduction. Fossil fuels were never 100% of the mix. The promised land is probably at least 50 times wind and solar in service and assume nothing has to be replaced after 15 years of serivice life, make that 25 years. My comments ignore reduced energy use but also population growth. We could assume a 4% replacement rate at the promised land. That’s a 25 year life for everything. So the amount paid for everything we bought to date that is still in service has to be replaced every year.

No doubt…Ive benefited from interaction with Judith Curry’s web site in my efforts to understand the issue of global warming and human induced change. Climate change is not an easy topic and many of us do not have meteorological degrees.

Having said that, Im not buying the paper presented as conclusive. Looking at 14,000 year old core samples is impressive…but not impressive enough as it may suffer from sample bias. Ice core samples provide data that go back 400,000 years. That time period shows a different relationship between CO2 and temperature (http://www.climateoutcome.kiwi.nz/latest-posts–news/co2-emissions-man-versus-nature71214). Meanwhile, the increase in CO2 of 10ppm over 200 years profiled in the article above is not impressive as it amounts to 0.05ppm per year. The last few decades have seen CO2 increase 2-3ppm per year. That is even more significant and troubling

The last few decades have seen CO2 increase 2-3ppm per year. That is even more significant and troubling

Why do you find it troubling? What is troubling you about it? What is the evidence it poses a threat as opposed to a benefit for the world? Note: temperature is not a measure of impact or threat. You need to state the net affect of all impacts to the world, not just selected negative impacts.